Animation on only part of the body

I bought a animation pack that has an animation for putting away weapons that's mostly moving the upper body, can I mix it with one of the run animations and have the character do both? Have run on the bone to the lower body and weapon switch on the upper or would I have to using something like blender to stitch them together and bring the new animation into the project?

 

You can use layers in your animation controller and avatar masks to achieve this:

https://docs.unity3d.com/Manual/AnimationMaskOnImportedClips.html

Good luck!