https://sims4studio.com/thread/8476/easily-make-pose-cas-accessory

Introduction This tutorial will show you how to make a pose pack that uses a CAS accessory. The accessory in this tutorial is karzalee 's Six Shooter, but you can use any CAS accessory that you want. If you have never made a pose before, please read the start to finish pose tutorial by orangemittens first.

What you will need Sims 4 Studio for Mac or Windows Blender 2.70 A CAS accessory .package

  1. Open the CAS accessory package in Sims 4 Studio.
  2. Click the mesh tab.
  3. Click the Export button on the mesh tab and save the .blend file.

  1. Open the .blend file that you saved in step 3.

  2. In the upper-left corner of Blender, where it says "Default", click the word "Default" and select "Animation" to switch Blender's layout to the animation layout. This is optional, but there are extra Blender features in this layout that are more useful for creating poses and animations and it gets rid of the UV panel that is not relevant.

  1. On the right side of the screen, you will see the outline showing all of the objects in the Blender scene including lights, meshes, and the rig. Next to each item is an icon with a cursor and one with an eye. Clicking the eye will show or hide the object. Clicking the cursor will make the object selectable or unselectable. By default, when you export a CAS mesh, the rig is unselectable to prevent accidental selection while editing the mesh. You will need to make the rig selectable again by clicking the cursor icon next to the rig. If you want to prevent accidentally selecting the mesh while you are posing, you can also click the cursor next to the s4studio_mesh objects to make them unselectable.

  1. Select the rig and change to Pose Mode. You can now begin posing your Sim. You can pose it just like you would had you exported your .blend from a pose package. You will notice that when you rotate the bones, the accessory will move with the Sim. Remember to set a keyframe at the end and save your .blend.

  1. Now that you have saved your .blend with your pose, you will need to create a package. Open Sims 4 Studio and, as usual, select the Clip Pack option and click Animation to create your pose package.

  1. Name your pose pack on the Pose Pack tab and then select the Clips tab.

  1. Name the first clip in your pose pack, and import the .blend file that you saved in step 7. You will see the name of your .blend to the right of the Export button. Save your package and place it in your Mods folder.

  1. Start the game. If your Sim isn't already wearing the accessory, bring them into CAS mode and put the accessory on.