If your motherboard came with any extras, such as Modem or network adaptor riser cards, or additional USB ports on a mounting bracket, now's the time to plug them into the board (consult your manual for the correct locations) and screw them into any free mounting brackets you may have.

Double-check all the wiring. Make sure all connections are firmly attached, and ensure that no wires are running close to the top of the CPU heat sink fan. You do NOT want to jam the CPU heat sink fan, especially with an AMD processor.

Double-check everything again. Now get all those loose screws out.