Photo Library won't open since installing El Capitan, how can I fix it?

[iMore Question]

Photo Library won't open since installing El Capitan

Previously had Yosemite OS. Since installing Apple Mac's new El Capitan operating system I can't open the Photos Library. How do I overcome this?

I've lost some iMovies. They're not there to click on. How do I get them back?

Was unable to send emails (received emails ok). I use @me.com. I seem to have overcome this problem.