Rain is a generic character rig you can use to learn and practice your animation sills, created by us here at the Blender Studio.
First off, ask yourself if you even NEED to link or append the rig into another file. Probably not! But if you do:
Then simply enter pose mode on the armature and start animating!
The rig is free to use, provided that the you respect the CC-BY license and include the credit: Rain Rig © Blender Foundation | cloud.blender.org
Check out a walkthrough of the rig's features in this video: