Help installing Windows 8.1

I'm going to be building a gaming machine and I have no clue on how to install windows because its going to have an ssd as a boot drive, a hard drive as mass storage, and because i have no optical drive I'm going to be installing it off a usb.

I'm supper confused and i'm starting to have second thoughts on this build so some help would be much appreciated

Your gunna need to make the Windows 8.1 disk into a ISO, I use PowerISO its free. Then your gunna have to make your usb boot able with the ISO on it. I use Windows 7 USB DVD Download Tool its also free. Your ISO name can't have any spaces or else the Windows 7 USB DVD Download Tool wont recognize it. I pretty sure I download it from my School server but you can find it on google.

Power ISO will work, but for free you can use the MS windows 7 bootable USB tool, it works for 8.1 too.

Once you have windows loaded I would put (depending on available space) all your most commonly used apps on the SSD, then just use the HDD for mass storage. You can also do all kind of stuff with caching on the SSD for the applications on the HDD, but since this is a gaming machine I'm going to guess that productivity bling like that isn't necessary or can at least wait until a later date.

tbh for your first build, i'd just make things easier for yourself and just temporarily salvage a DVD drive from an old pc or something.