Adding an additional library.
Adding an additional library to a Page or Album.
Add an Additional library to a Page or Album on creation or editing it, navigate to the the Advanced tab and selecting it from the Library drop down under the Additional libraries section. Saving your changes will apply it to the page or album.
Appling multiple libraries
Multiple libraries can be applied by adding another drop down to select from with the Add Custom css/js library button.
Removing a library
You can remove a library by clicking the Remove button above the specific Library you want removed.
Adding an additional library to a Theme.
You can add an additional library to a theme when creating or editing it. Navigate to the Additional libraries tab, and select the Library you want to apply from the drop down, saving you changes to theme will apply the libraries you've selected.
Similar to Pages and Albums described above, multiple libraries can be applied or libraries can be removed.