How to add an already created animation and throw a projectile?

I would like to take a sling animation I already have created and add it to the third person controller asset and add an attack state and blend tree with attacks (I'll save a different controller for each character unless I should just create a different blend tree?). I want it to prime or loop the animation for the sling attack until they release the RT button on my xbox one controller. I really like the shoulder look on Ellen's below but want a different targeting system with a line to show where my stone is hitting at.

Notes: I have the sling as a separate object in the characters 3d scene. might need to show how to attach in unity to a hand during certain script operations if showing a script. Also, unity version 2019.3 thinking about going to 2019.4.

For the adventurous, I would like to create something similar to the Ellen abilities system too but I have simple animations for my attacks as they are hack and slash type animations. For example, I want the sling throw to just be faster and do more damage for one special attack. If you have tutorials on a simple version of it or where the source code is for it, I can take a look at it.
I really like the ability system here (I'm using timed abilities or abilities based on stamina availability.):
https://learn.unity.com/tutorial/im...ystem-training-video#5eea8ad8edbc2a002071fce7