How to constraint an object in an animation

video: https://gyazo.com/fc1d5ddbdb88c46e1a326babe9122440
i want to accomplish what is seen in the video where the tool is constraint to the arms in diffreent sections of the animations.
i have seen this tutorial saying that can be done using blender.
i use moon animator and want to know if i can constraint it easily as shown in the video.

erm well, the tutorial says to weld it to the torso. So… weld it to the torso. You would just have to anmate the gun separately as seen in this video

i know i have to weld it to the torso, but to have it on the arm blender constraints are normally used. do i have to use blender or does moon animator have that feature?