Unless you are a team leader or an admin, I’m afraid you can’t.
If you are a team leader or an admin indeed, then you can change your team’s skills from ‘My company’ page > ‘See profile’.
To adding a skill, once you are on the user's profile, just click on the "add new skill" button.
To delete a skill, just click on the delete button (the bin icon). Remember that you can't remove a skill with active learning paths. Wait for the user to finish them, or move the paths to the "other" column.