boot camp won't recognize my windows installation disc

so i downloaded windows 8.1 pro offline (from the microsoft site) the other day. i know windows 10 just came out but i'm only wanting to run paint tool SAI which doesn't have a lot of updates ever and the people at best buy told me 8.1 pro should be fine. so i downloaded it, burned it to a dvd, made the iso and all the steps in boot camp ran fine (with a few little bumps) until the last step listed; install windows 7 or later. it keeps saying "the installer disc could not be found" but my computer recognizes it's there and shows it in my finder but nothing special pops up to help me continue on and finish my installation. i'm completely stuck and have been searching the internet for hours to no avail. someone please help me. thank you