In order to do what you’re looking for is a little setup. You need to get the Mannequin skeletons. In order to do this you need to make a UE5 project with Third Person Template selected. Export the Mannequins into a Folder somewhere on your PC. Delete that project (unless you want to keep it) Create a new Blank project. Import new asset, select the Mannequins you exported. They’ll import with their default Skeletons. All you’ll end up with are the Default Mannequin Meshes, Skeletons and possible the Physics Assets assuming you left the import settings default.
After that, you’ll need to figure out the setup for your live link motion capture settings to animate the skeleton for your live stream.