What can I do about getting eyelashes and eyebrows to grow? I don't have either

Without knowing the cause and if the areas are thin or completely gone it's impossible to recommend you anything to help promote growth in those areas.

You'll want to see a dermatologist to first determine the reason for the eyebrow and lash loss. Depending on the exact cause different treatments would be advised.  Alopecia areata, traumatic loss, trichotillomania, frontal fibrosing alopecia, toxin use are all possible diagnoses and the treatments are very very different depnding on which one it is.