In view of the fact that you are honest enough to admit, that you have no real experience of building a computer and using the guide my good colleague phillpower2 has sent you, MAY I suggest that you DO NOT gain the experience on your NEW BUILD of the parts you buy for this computer.
It is not difficult, these days, as it was in past years, as most connections to the motherboard are block connectors, with a blanked off or offset pins and providing you take reasonable care it is not as easy as it once was to make a mistake.
NEVERTHELESS it can still be done, and just a couple of months ago on this site, a person posted a problem, where the computer would not even boot, after his new build.
He had it transpired connected a POWER IN to a power out connector on the motherboard for a fan.
He consigned TWO motherboards to the scrap bin., making the same mistake twice.
MY strong advice is to obtain, even if necessary by buying, a computer that is past any real useful like, but working.
Possibly a friend or acquaintance may have one.
TAKE the computer completely apart.
Reassemble it. If it still works all is good, if it does not, then clearly something is wrong.
This old practice computer may well not be a copy of your new build, but the experience you gain will be invaluable.
I would say, in addition to the above that these are your main points to guide you and the main risks you need to avoid.
1. Take your time, there is no point in rushing the job. There are no prizes for speed.
2. Choose a time when if possible you will not be interrruped, even by telephone calls.
3. Your working area, should NOT be on a carpet or another static inducing surface. AND you need good light.
4. Before handling any components, take anti-static precuations - explained in the link.
5. When you buy the case, it normally comes with a packet of screws and other small parts. Stand - off posts for the motherboard. SORT these out into their various sizes and keep each group separate in sutiable containers.
6. EXAMINE carefully the location of the securing points for the motherboard and match those to the positions on the case - motherboard mounting area, so that you are SURE that stand-off posts are ONLY inserted into the case in those positions.
ONE stand off post in the wrong place can IMMEDIATELY consign a motherboard to the scrap bin, as soon as power is supplied.
7. Assemble the CPU and the cooler and fan on the board BEFORE putting the board in the case. NOTE this is the best way normally, as the force needed, although not great to install the cooler is usually best applied before the motherboard is in the case. ENSURE you are working on a level, surface and are not straining the board.
8. Generally it is best to install the PSU, especially if it is an upper mounted PSU, before the board, as if of course it slips from your hand onto the board, it MAYBE an expensive slip.
9.When connecting the main 24 pin power supply connection to the board and it is normally near the edge of the board, SUPPORT the board, on the edge. DO NOT forget the CPU power and the fans connections.
10. The motherboard will come with its own I/O plate, (Input - Output) for mouse, keyboard - maybe USB connections, sound connections, LAN (Network) and USB ports. This must be placed in the case and if one is already fitted, that one (the pre fitted one must be removed.)
11. If you are installing a graphics card, ensure that you know where this is going to be located on the rear of the case from its position on the board and remove the blanking plate in that location, BEFORE you install the board. This is VITAL on the cheaper cases where that blanking plate has to be broken away from its securing points. It is still best to do so, however on most cases where the blanking plate is frequently ona block of them, released by one securing clip or screw.
12. Depending on the type of case it is also usually easier to install the Optical drives DVD/CD and leave them temporarily secured by one screw, fastened only touch tight, before you install the PSU or motherboard. The fitting of these drives requires you usually to remove the blanking plate on the front of the case, and to do that the front panel has to be removed.
TAKE it slowly and carefully you will not be the first person to break one of the clips on the front panel.
13. The HDD inserts into its slot from the inside of the case. Take care with this and the optical drives that you do not mix up screws, as too long a screw in a HDD, will in some drives, damage the drive beyond redemption.
Some cases are cllips for the drive, which simply twist and lock and you do not have to use screws.
There are many other points and all you have to do is ask and someone will be here to help.
MY FINAL comment is that this is not a job where you can read the manual AFTER you have installed the motherboard.
I would urge you to read it at least twice before you start and check the connections from the PSU to the motherboard, to the HDD and the case connections to the motherboard for the USB, the front panel audio and the front panel header where the power, rest and leds connect VERY carefully before you start
FINALLY good luck