The Transportation Center Parking Garage is the most convenient place to park when going to the Convention Center. For your $6 you get covered parking and an enclosed walkway directly into the Center.
The Reibold Garage is also available and costs about the same. You’d have to walk about half a block and cross Main Street.
There may also be on-street parking within a few blocks of the Convention Center, and there are surface parking lots. It is not necessary to pay the parking meters on weekends.