Adjusting "Blind Tension on Nuevo ES"

Does anybody know how to adjust the tension of the blinds on the side windows of a Nuevo ES, my off side blind keeps sliding half way down the window whilst I'm driving.

Thanks

are these the concertina type blinds?

Hi,

I described the fault incorrectly.
I do Have concertina blinds which come up from the bottom but it is actually the Fly Screen which comes down from the top which needs re-tensioning.

I found instructions for the Heki roof light blind re-tensioning on the Heki website. Check the window manufacturer's website.