When you say “you linked the armature”, how did you do it? If you went in the armature folder that that’s the problem. If you linked the armature object or linked a collection with the armature in it then you’re good. In most case you want the mesh to come along so collection method is the best. Once you make the library override select the armature and ctrl+tab to switch to pose mode, select the bone, and then click the bone constraint tab(The chain link with a bone icon at the bottom) of the properties editor. You can also use the shift+ctrl+c hotkey just like normal.
