While you cannot edit or delete the default skills and skill categories that come with the system, HandsOn Connect allows you to add new skills to the skill profiles used by volunteers and volunteer opportunities,

If a contact already has login access in some other role (Volunteer, Partner Staff) you'll first have to disable their current license before you can change them to a Volunteer Leader profile.

If they have no access, you can skip that step and simply grant them access directly as shown below.