Royal Windsor390 awning

Since no one else has responded, all I can offer is that it looks very similar to our Kampa Air Pro 390.  With that - start off by pegging the corners nearest the van, slightly underneath the van so as to get a good seal with the foam pads against the side of the van. It's quite important to get the foam pads as near vertical as possible - if not, the awning tends to look a bit of  mess and is all out of square. Then inflate the tubes - ours has just one inflation point so that's easy but yours may have more. Then peg out the other two corners, making sure the doors are zipped up, thereby not over-stretching the door zips. Also make sure the front is pulled tight across the front - in your photo it looks a bit baggy! - and that it's all square. Peg out sides and then lastly the front.  One tip is to make sure you kick in the bottom of the two middle poles so that they are in line with the corners.  If it's like ours, they tend to splay out initially but by doing this, you will push the roof upwards slightly, thereby eliminating any pooling on the roof.

Hope this helps.