How do you loop FBX animations I have a 39 frame walking cycle from Mixamo and I want to keep looping it through but not where he keeps going back into his first position. I am very new to character animation in Blender so I really can't find how to do it. Thanks!
Here's a video explaining how: 
https://www.youtube.com/watch?v=KgPDe2GoiRY

What you want to do is open the graph editor, and select the keyframes that you wish to loop over (over their respective time period), press Shift + E, and select "Make Cyclic (F-modifier)".