Normally there are two "wheels" one at each end, that have to be spun loose and then swung down to release the awning, and then likely a safety lock (swinging hook that engages a bracket with a hole in it mounted on the awning metal cover. I don't think all trailers have that but if yours has one it should be near the rear support arm.
So the two wheel locks and the safety lock if installed need to be opened first - presume you have done that!
There should be a strap loop poking out from under the metal cover about mid awning for you to hook with a pull rod and so to pull the awning out.
If there is not, perhaps it has broken, or perhaps the previous owner didn't take care in rolling the awning up and it has vanished inside.
In that case, try getting upon a step ladder and pulling the top of the awning support arm away from the trailer, that "should" allow the roller tube to move out unrolling the awning.
On mine, the safety catch had not been installed correctly and sometimes teh hook - even when in the open position - would catch on the metal awning cover and stop the awning from unrolling even though I had the pull hook properly engaged in the strap.
I wound up having to modify the rear support arm slightly (drilled new hole to raise the back end of the awning roller tube slightly) to resolve this. Works fine now!
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.