Updating a motherboard
It should boot, and you'll see your new motherboard's splash screen. There, check the drive and RAM configuration to make sure everything's recognized, set the boot-device priority, and enable USB 2.0 or PCI Express support, if your board requires it. Then, assuming you aren't reinstalling Windows, boot for the first time.
Windows will need to install drivers for the motherboard, most of which it can and will do automatically, though you might need the CD that came with your board.
(Sticky notes work well.) Many of today's connectors are color-coded, but if yours aren't, this precaution could prevent frustration later.
Slide each expansion card into its appropriate slot, and screw it down. Most interior cables are keyed to connect only one way, so replacing them should be easy.
If you're unsure where certain connectors live on the new board, consult your manual for a diagram.
For your power/reset switches and activity lights to work, you need to match up the connectors with the proper pins and orient them correctly.
Your motherboard manual will explain the proper layout, but a little trial and error may be required. Finishing up Close the case, re-attach the rear-panel cables, and turn on the computer.