You can use After Effect’s built in Lights to Light your scene. There are 4 different lights to choose from, as they all can affect your scene differently. Go to Layer/New/Light to create a new light, and from the pop-up then you can choose what kind of light to use. Element can use up to 8 lights in a scene. There are also built in Element lighting presets to very quickly light a scene, see Render Settings/Lighting.
General light with a spherical falloff
Light is infinite in a single direction
Cone shaped light that focuses on radial area
Lights evenly infinitely. Normally good to use as a fill light at a low level.
Mixing all kinds of lights at different intensities help to create more organic and fully lit scenes.