How can i add more animations to a downloaded asset?

i downloaded an animated arm asset, and it only contains some basic animations like swinging and running, so i wanted to add Gun animations (i can make the animation via unity3d, i just dont know how to add/attach the animation to the gameobject) but inside the animation tab, there’s no create a new clip or anything like that. any help?

It’s not what you want to hear, but in the long rong you’re better off doing all modelling and animation work in a dedicated 3d modelling program like Blender.