Hi Steven, welcome to Fantasy Football.
Regretfully, it is currently not possible to draft a Head-to-Head league that contains an odd number of teams. Due to scheduling and tiebreaker complications, all Head-to-Head leagues must contain an even number of teams.
If you wish to have 13 teams in your league, you would need to use a "Points Only" or "Rotisserie" scoring format, with no head-to-head schedule.
Thanks,
Scott