The BIOS is on your motherboard, so is unaffected by your changing your OS and/or HDD. Before you connect your HDD (disconnect it if it's already connected), boot to BIOS and set your boot priority to your optical drive (ODD) or USB (whichever you're going to use to install Windows) then save, exit, and power down. Then connect your ODD or USB and HDD and power back up. It should boot to the Windows installation menu.
Make sure you have your Windows activation key written down and available before you do this, as a clean install will overwrite anything currently on the drive. If you use a USB, plug it into a USB 2.0 port, not a 3.0.