Does anyone have any tips or webpages that give good instructions?

I have planted several of these plants because they are fasting growing and provide lots of color. However, they are also rather invasive (depends on how you define fast growing...lol) and thorny. I do not want them to get out of control.

I am hoping to train them into a tall shrub ot even sort of a tree. Perhaps like a topiary with just the round or squared top section.

Nothing complicated. I just want to know when and how to cut the branches to keep it in check. Any suggestions greatly appreciated.