Joining the group is a matter of just clicking on the join request. You do not require approval to join.
After you join the group, you can submit 2 works of art each day as a member. If you somehow find that this isn't enough, you may contact The-Ketchi and request the 'Contrubutor" status. If approval is given, you will be allowed submit 4 works of art each day. Approval of this will require significant and consistent submission of cards to the group.
Submit works of art to the Featured Gallery. One of the group moderators (Co-Founders or The-Ketchi) will place it into a suitable gallery folder depending upon its playability.
Submit anything Pokémon, Magic: The Gathering, or Yu-Gi-Oh! card related that includes My Little Pony themes and/or characters, regardless of generation or format.