Hi Joshay,
First thing to do is to power off your PC, unplug it from the wall, and then make sure all of your cables are plugged in correctly. Especially make sure your SATA power cable and SATA data cable are both securely running to your hard drive.
From there, if you turn on the PC and still get stuck in BIOS look for the current available boot drives. We'll need to know if you can see any of your hard drives available in the BIOS.
** Also note, when you install a new motherboard it is highly recommended to re-install Windows on your old hard drive. If you have an OEM version of Windows it is tied to your old motherboard and you'll either need to buy a new version of Windows or contact their customer support to see if they will unflag your old key for you.