The version of iPhoto you have is too old.
Starting with Yosemite or El Capitan (can't remember which), you can ONLY use the LAST VERSION of iPhoto, which is 9.6.1.
NO EARLIER VERSION WILL RUN.
Apple does not make it easy to get this version.
You can try this:
1. Delete or move the older version of iPhoto from your applications folder
2. Go to the app store, to "purchases", and see if you can re-download iPhoto
3. IF the app store lets you do this, you should receive version 9.6.1, which does run.
IF THE ABOVE DOES NOT WORK:
You can still run iPhoto 9.6.1, but you're going to have to get it from "unauthorized sources".
It CAN be "found and downloaded", and it works.