Hi, I also get early 30s mpg average, but have seen 41mpg on a run when feathering the throttle and minimal break pedal use.
I had the same message about the tyre pressures. Power the car on (without brake pedal, I think) then press the tyre pressure initialise button for a couple of seconds and the dash shows a tyre initialisation message. A few seconds later, it should be ok.
The button is under the dash above the brake pedal. As Michael says, just consult the manual.