Chinook RV

I have purchased a pole and rope awning from vintage trailer supply for my 1975 chinook concourse. I ordered their awning rail as well. I am very new to this having owned my chinook for a month. a very happy month !!!

I am concerned about how to mount the awning rail to support the awning. Am I able to screw the rail near the roof line? any advice to this newbie will be appreciated. I love this board !!