Apple's new photo application makes it easier to move your photos library from one location to another. For a quick walkthrough guide on how to do this, just read the write up below.
Note: By default Photos saves its library in your Pictures folder.
If you want to know exactly where your library is, you can open Photos and then “Preferences” (“Command + ,”), and the “General” tab will show you the location, which you can then open in Finder.
Click the the “Show in Finder” button and here’s where your “Photos Library” is located.
To move your Photos Library, drag it to its new location, double-click it, and the Photos app will now point to it.
Creating a New System Photo Library
There are any number of reasons you might want to create a new system library in Photos. Maybe it’s become corrupted and Photos won’t open, or maybe you just want to start fresh and archive your old one.
Regardless, to create a new System Photo Library, first open the location where your current system library is and drag it to a backup spot if you want to keep it (recommended). Drag it to the Trash if you don’t.
Next, open Photos, which will spur the following prompt. Click “Open Other…” to either find an existing library or create a new one.
Here’s the “Choose Library” dialog. If you have other photo libraries on your system, they’ll be listed here. If you want to find an existing library in another location (such as the one you just backed up), click “Other Library…
Since you want to create a brand new library and populate it with pictures already stored on iCloud, click “Create New…”.
Now the Photos application opens to an empty library with ways to add photos to it: you can import them from a camera or memory card, import them from a location, or drag pictures directly into the application.
If you want to sync this library to your iCloud account, you have to first convert your new photo library to the “System Photo Library”.
Remember back on our General tab there’s a “Library Location” option? Click “Use as System Photo Library” to convert the new library and enable the iCloud features.
Now, if you click on the iCloud tab, you should see that your stuff is syncing and will be restored to your new Photo Library as soon as it’s downloaded, while anything you add will be uploaded.
Credits: guide by how-to geek.