You should be able to find the Animation Composer in the After Effect's menu under "Window" -> "Animation Composer."
If you have installed Animation Composer and it is missing in the Window menu, try the following solutions:
Possible solution 1:
Restart After Effects.
There might have been an issue when opening After Effects from Adobe Premiere that has caused the plugin not to load.
Possible solution 2:
- Follow this uninstall guide to remove Animation Composer manually.
- Install it again.
Make sure that you are launching the same version of After Effects that you have installed the plugin into. Sometimes the installer doesn't list your version of After Effects during the installation step. If this happens, you have to locate your After Effects installation manually with the "Browse" button.