First off you need to check all coax cable connections.
The one on the antenna head, the one on roof connection, the one inside antenna ceiling crank assembly, the ones on back of antenna wall plug/dist. box (if so equipped) and the ones on TV.
Then check that you have 12V DC power to antenna head (center pin to outside shield on coax cable) with booster ON
With good connections and 12V DC power you then have to 'AIM' the antenna head towards the TV transponder towers.
Which way to 'aim'......check which way other campers are pointed or use an antenna website for direction or install a signal meter.
Some antenna websites:
Antenna PointDTV Reception MapAntenna WebAfter you 'aim' then TV input has to be set to 'Air' 'Antenna'
Then do a scan for available channels
You have to aim and rescan anytime you change locations