You are almost there! All that is left is installing your operating system.
Now that your BIOS is setup, you can go ahead and restart your computer with the OS disk inserted into the drive. Since you have set your BIOS to boot from your ROM drive first, it will automatically read the disk and try to load your OS from there.
The computer will boot into a Windows 7 (or whatever version of Windows you choose to install) Setup screen. Simply follow the onscreen instructions to install your operating system. Once installation has been completed, your new computer will be good to go!