/3/ - 3DCG

Hoe can I add the mesh with bones on the left to the armature on the right?
I'm trying to replace the mesh of one gun with another. The blender on the right has the rig with all the animation tracks that I export to Unreal. If possible, I'd prefer to just replace the old mesh with the new one and fix up any animation problems rather than start from scratch with my root template, but honestly I've had such a hard time trying to get this to work that I'd be extremely grateful for any information that helps me get the new meshes+bones into existing armatures