The extra parts included in the kit are not used on the Cali awning, just the semi circular plastic cups screwed on the inner parts of awning cover rail and the bracket at the front of the van part of the main frame as shown in the diagram posted above. The rear rail just secures on the existing projecting machine screw at the rear bracket.
In practice you just extend the awning fully until the fabric goes slack and fit the rails, then re tension the fabric to secure the rails. This has worked fine over the three years I have had these side panels withstanding quite strong winds/heavy rain. I secure the base of the legs with decent pegs and tension ropes to the tops again to substantial pegs. Always lower one of the legs to ensure rain drains away if left up.