To import the rig into your project file you can either,

1. Click append>navigate to the rig file>go to collections>select the MASTER collection.
2. Click Link>navigate to the rig file>go to collections>select the MASTER collection>in your project file, right click on the collection in the outliner>select, Library override>make>selected and content. 

Version 1.2 update.

All rigs have been updated for Blender 4.