Q: Update OS X Yosemite

I updated my MAC desk top OS X Yosemite, and now the I Photo App is gone.  I don't know how to get to my photos. I tried to update I photo, but it said it isn't available.  When I click on the photos tab, it tells me that there isn't enough disk space to migrate my library.  I'm not sure what to do.  Please help.

Thanks