Q: no 'Install windows 7 or later' option but 'remove windows 7 or later'

Im having a seriously problem with my attempt to install windows 8.1 on my iMac OS X 10.10.4. I've tried almost all the tutorials available but I still can't do it. It just doesn't work for me after I have installed all Windows support software where it should bring me to a partition window where I can 'equally divide my Mac hard drive with windows' but it only shows http://gyazo.com/d657674c47e78300bcc171a7a6d1e282. There should be windows for me to split the memory between.

I've formatted everything properly e.g. formatted my external drive to FAT. [I have not yet partitioned or anything since the tutorials does not tell me to do so.]

I really need help ASAP. Thank you.