When creating aim constraints, you can first set creation options and then create an aim constraint, or you can immediately create a constraint with the current creation options.
The default constraint options work well for constraining objects so that they aim along their local rotation positive X-axis.
To add an aim constraint to an animation layer
Turn on Maintain Offset when adding constraints to animation layers so that your constrained objects do not move unexpectedly.
The constraint animation is now contained in its assigned animation layer, and it contributes to the result animation in your scene.