In the dashboard, tap on "View" next to any of your live ads to make edits.
Next, tap on "Edit Campaign" to make changes to the way your ad looks.
NOTE: Your Instagram ad text utilizes line #1 on your "Edit Campaign" screen. You'll want to make updates to line #1 in order to update your Instagram ad.
Once you've completed your edits, click on Save Changes to finalize your campaign.