Install windows on a second hdd drive (mbp a128)

Dear community,

recently I changed my dvd drive against a second hard drive (with a build kit from amazon). Now, I would like to install windows 8.1 on this new hard drive to change through the operating systems (to be honest, windows is way better for games, especially the old ones).

So far, I bought a windows 8.1 license, have an usb-stick ready and already downloaded the windows image. I also tried to use boot camp, but I think the missing dvd drive confuses the system. I thought, that I could easily create a bootable usb-stick with windows on it, restart my system choose to start from the stick and an installation on a choosable hard drive can start, but I guess that's way to simple.

Can anybody explain me what I have to do?

Best regards,

Richard