No worries, did you get the yellow luggage tags and the instructions for DME?
If so the instruction sheet has a bar code on the bottom you can use that to check in for DME.
If not (and you have already made a DME reservation) just go to the DME counter and they will verify your reservation and print a voucher for you to board the bus.
If you didn't make a reservation for DME give them a call now to save time at the airport, you will still have to stop at the desk to get a voucher but it will be quicker.