If you just have a single i Photo Library, Photos will do the work automatically for you.
If you have multiple libraries, you'll have to choose which one you want to import. If you're upgrading to Photos for OS X from i Photo and you've only ever had a single i Photo library on your Mac, your upgrade path is easy: After you open the app for the first time, Photos will automatically import all your i Photo images into the app.
Photos for Mac has a similar setting to help you optimize storage on your Mac.
Update: this guide/method also works for OS X “El Capitan” (10.11) click to enlarge After Photos came out, you might have noticed that i Photo no longer wanted to run. Once you have i Photo working again, maybe you’ll want to take a closer to look at Photos. Regardless – here are the steps to turn i Photo back into a functional App.
Apple is sending a clear message – i Photo is gone.
You get only 5GB for free, which even the smallest of libraries will quickly exceed.
Pay plans start at 99 cents for 20GB and go up to $19.99 a month for 1TB of online storage.
Your old i Photo library will still remain if you need to use i Photo for whatever reason, but changes made to those older images won't automatically sync to your new Photos library.