There will be a line at the smart gates for people who are eligible but haven't registered yet - go through there, scan your passport, look at the facial/eye scanner, then you'll be directed to the immigration officer who will validate it so on your next visit you can use the registered line which has no immigration officer on the other side. No stickers or barcodes etc on your passport.

If you want to register your Blue card for e-gate, after exiting customs, turn left - so if you have chauffeur drive, it may be best to go and pick up your chauffeur drive voucher first - and then before you reach the doors, turn left again and go to the far end of the arrivals hall, past the baggage office and toilets, and there will be a DNRD office. On the left hand side is a Q-matic thing, press that, select the option for e-gate activation/renewal, wait for your number to be called. When called, go to the desk, give the person your passport, scan your finger prints etc. Then you can use the registered lines for smart gate - and also use e-gate on leaving DXB. iirc there is no charge for a Skywards card e-gate activation. You will of course need to be a GCC citizen, UAE resident or visa-free national to be eligible.