The Convention Center North Building is located south of Monroe between 5th Street and 3rd street. There are two garages that are easily accessible; both are $12 / day:

North Building Garage (see #4 on parking map)
Enter on Monroe between 5th street & 3rd Street.
Follow signs to the Food Court.
Take the elevator to Level 200.

Convention Center West Building (underground) 2nd Street just south of Monroe. (see #1 on parking map)
Enter at the northeast corner of 2nd street.
After parking, follow the signs in the garage to the Convention Center entrance. Cross 5th Street to the North Building
Take the elevator or escalator to the 200 level.

The Heritage Science Center Garage (see #2 on parking map)
Enter on Monroe between 7th street & 5th Street.
Cross 5th street to the North Building
Take the elevator or escalator to the 200 level.