Before we begin with this Tutorial, please note that Custom Poses and Animations are not officially supported by EA/Maxis so use them at your own risk!
The Sims 4 Custom Poses and Animations can be installed the same way you install Mods. Download a Custom Pose or Animation (That you can find Here) and then Paste it in the Electronic Arts\The Sims 4\Mods folder. (Click Here for more info about installing Mods)
Each Pose/Animation overrides an exisiting Trait Animation that can be selected in CAS. For example, the Vogue III Pose Pack replaces the Clumsy Trait animation.
To start a Custom Pose or Animation, just select the Trait that contains that certain Pose/Animation. Since Trait Animations are very fast, its recommended that you change the CAS clock speed to low values (Cheat: casclockspeed [0–10] ; Example: casclockspeed 0.06).
If you want to repeat the Animation again, just select the hexagon where you added the Animation Trait.
Create your own Poses by downloading The Sims 4 Pose Player HERE!