Follow the signs for baggage reclaim. There should be really only one path as everyone must pass through customs
Get in line for "All Other Passports"
After going through customs at UK Border follow signs to baggage reclaim then follow signs to Exit
Go through the Nothing To Declare line
Look for the elevators that take you down to Underground (with red circle logo)
Take the elevator down to (-1) floor.
Before you go through the turnstiles at Underground station find this machine to left
Tap "Buy New Card"
Tap 10 pounds
After you get your card head through this machine gate by holding your Oyster card on yellow circle. Green light should come in there and gate will open. Take this one train for quite a few stops.
Exit at South Kensington Station. Follow "Way Out, District and Circle Lines" signs.
Follow signs to District and Circle Lines
You want to be on the Eastbound side of the platform
Wait for the train, then get on. Ride this to Temple stop. Exit Temple and follow "Way Out" signs up to surface. You will need to swipe your Oyster card once to exit. I will be there.