You have two choices.
You can take your bags to the RAC desk from 5am to 1pm, AND not earlier than 12 hours before your flight and NOT LATER than 3 hours before your flight, check your bags with them, then board the DME bus at the time designated on the paper they place on your door the day before you leave. RAC will transport your bags to the airport.
Or you can store your bags with Bell Services, then retrieve them before boarding the DME bus. They will be stored under the bus by the driver, then you check your bags at the airport.
Either way, you need to be at the DME bus stop ready to go with everything going on the bus with you at least 15 minutes before the time on your DME paperwork.
If you have to retrieve something from Bell Services before boarding the bus, allow an additional 30 minutes.