How to make an animation

I want to apologize about this page being so ugly, this is just a wall of resources which you would normally be expected to find yourself.

You can either use Blockbench or Blender to animate the player.
You will need the GeckoLib plugin for BlockBench in order to animate the player that way.
The base models for both Blockbench and Blender can be found here.
If you want to use blender this might help.
You can bend some bones when bendy-lib is installed.
You can get help with all things playerAnimator related here.
This provides some information about animating in Blender.
You can get help with Blockbench here and maybe here.
Once you export your animation you have to place it at the assets/<namespace>/player_animations directory and that's about it. (With namespace being replaced with your mod ID)

Important

THE NAME OF AN ANIMATION USED TO ACTUALLY PLAY IT IS THE ONE WRITTEN IN THE FILE NOT THE FILE'S NAME!