Apple is sending a clear message – i Photo is gone. Following these instructions, you’ll have i Photo working in Yosemite in no time.If you still have the demo version hanging around on your Mac you can use it to upgrade to i Life '11 without having to purchase the newer i Life suite.
(The instructions are the same for i Photo '09.).
You can also use Time Machine or a favorite cloning app such as Carbon Copy Cloner.
While Photos does not currently have all the bells and whistles i Photo had, it is continuing to add features with each update.
It also has the advantage that it is included with OS X El Capitan and the newer mac OS.
Before you install any i Photo upgrade or update, you should back up your i Photo Library. There was a problem with the initial version of i Photo '11 that caused some individuals to lose the contents of their i Photo Library during the upgrade process.