How to set up weapon Pose+Animation?

I am using 4.13 with the sci fi dark pack and a few anim packs such as the rifle’s and starter anims. What I need help with, is just setiing them up. In more detail, I would like to learn how to add the gun the my character while switching to the correct set of animations for that gun. I have asked questions before but to no avail. if youu have time, please help, if even for one aspect of the question.