First add your hard drive and optical drive.
Then add psu + screw it in
Add copper risers into case
put in i/o shield if you haven't done so
add motherboard with ram, cpu, cpu cooler already installed (do this on mobo box prior to all of this, remember to add thermal paste)
Once inside, screw in the motherboard, do not screw in all the way (until you feel pressure)
Now add gpu and wire everything, then turn on computer check bios and see if everything is in ship shape, then install windows and enjoy