problem to install win8.1 on osx 10.9 (mavericks)!?

I have an Early 2011 MacBook Pro (MC700: core i5,13.3").

Bootcamp Assistant(5.1) can't find or recognize my win8.1 DVD (in step2 of wizard)!

Why?

How can I do?

Is possible to install win os without bootcamp assistant?

Is this version of BootCamp compatible with Windows 8.1?