You can park at the meters on the streets around the church, but we recommend the Laclede Gararge at 3634 Laclede Ave, St. Louis, MO 63108. Grab a ticket upon entering. When leaving, tell the attendant the name of the bride and groom and they should let you out without paying. The garage is about a 5 minute walk from the church. There is a drop-off area right in front of the church.
There is plenty of free parking right outside of the venue, so you shouldn't have any issues finding parking.