Can I put my accepted-but-not-yet-on-IEEEXplore paper online?
As the comment from  Nate Eldredge said: read your copyright agreement and ask co-authors. 

You can definitely list the paper in your publications if you mark it as "accepted for...". If the admission committee is interested in reading it (often it is just interested in the title, unless this is the summary of your previous work), they can ask for it.