Bootcamp Yosemite: How to Install windows 7 with DVD
The answer really depends on the model of your Mac. Generally, if your Mac came with an internal optical drive, you probably should install using the DVD. Also, the Boot Camp Assistant is a good source to answer your question. If the option to create a Windows install USB flash drive is available, then you probably will need to create an iso file from your DVD. Start the Boot Camp Assistant application and continue through the windows until you get the "Select Tasks" window. Your answer will be based on the options that appear.