So basically any video you see on PC building has these few steps:
1 Assemble the motherboard.
1.1 Put the motherboard on the box it came in. This will act as kinda a soft barrier, as well as mostly clean environment. MAKE SURE TO TOUCH YOUR COMPUTER CASE (IF METAL) OR GROUND YOURSELF SO YOU DON"T FRY YOUR SYSTEM!!!! IF YOU GO THE ROUTE OF GROUNDING YOURSELF OFF THE CASE, DO IT OFTEN!!! Or you can get an anti-static strap but that will just cost more $$$.
1.2 Put the CPU in the do-hicky where the CPU goes MAKING SURE TO NOT TOUCH THE PINS ON THE BOTTOM, making sure it's in the right orientation where the corners with arrows match. DO NOT FORCE IT, AS IT SHOULD SIT NICELY IN THE SLOT.
1.3 Move the pin/holder down to lock the CPU into place, but it varies depending on the motherboard. It might take a little force to push it down, but just be cautious every step of the way.
1.4 Put the RAM sticks in, making sure it's the right orientation where the little notch in the almost-center of the stick matches the notch in the RAM slot, and when you push the stick down 2 little clips on both sides of the ram should click/pop upwards, locking the ram into place. NOTE that the little notch is not directly in the center, it's off to one side a small bit. IF YOU HAVE MULTIPLE RAM SLOTS (I.E. GRAY AND BLACK SLOTS) MAKE SURE YOU PUT THEM IN THE CORRECT CHANNEL THAT YOUR MOTHERBOARD REQUIRES, AS WELL AS PUTTING THEM IN THE SAME COLOR SLOTS (BLACK TO BLACK, GRAY TO GRAY, etc).
1.5 Apply your CPU cooler, which varies on which cooler you bought, wheather it's just a heatsink or a watercooler block. Just be super careful with the thermal paste as you don't want any air bubbles or to constantly move it as you might cause cooling issues later on. BE VERY CAREFUL TO PUT IT ON THE RIGHT WAY OR ELSE LORD VADER WILL CHOKE YOU! Don't forget to plug the fan cable into the motherboard too!
2 Case Assembly
2.1 Pop in the IO shield, making sure not to bead/break it, but it might take some force to put in.
2.2 Radiators/fan installment, but depends on if you are adding fans or have a watercooler setup.
2.3 Carefully lay down your case and place the motherboard inside. CAREFULLY PLACE IT IN, AND DON'T OVERLY TIGHTEN SCREWS AS IT MIGHT DAMAGE YOUR MOTHERBOARD.
2.4 Attach PSU (Power Supply Unit). If your motherboard gets in the way, you might want to install the PSU first. I had to with my sisters computer.
2.5 Install the Graphics Card, after removing one or two of the metal plates on the back where the PCI-e lanes are, then ensuring to screw down your graphics card where you removed the metal bits, as you should see some screw holes on where to do it.
2.6 Make sure all your cables are plugged into their respective locations, also making sure your HHD(s), SSD(s), optical drive(s) are situated where they should be. Sometimes you might need to install them before the motherboard, but it comes down to how much room you have to work in within your case.
3 Start 'er up!
3.1 It should auto-boot to the BIOS screen, but if you get any error code(s)/message(s) just google your motherboard and the error code and you should find a way to fix it.
3.2 Install windows by selecting your boot drive (i.e. an SSD) and just go through with installing it.
4 Cable management if you choose to do so.
I might have skipped a few steps, but I think I outlined how to do it, and stating the warnings/cautions while doing so.
Try to keep those cautions in mind while watching a video on how to build a PC (as my guide didn't have pictures/detailed how-to). (In case I missed something, someone should provide a solution and I'll add it to my basic guide.)