I'm sure you can just add it to what's there. It will out-compete most things in my garden for space. Once it gets going it will offer your ivy some shade, which will help it to get going better, too.
It shouldn't need any support, just plant it near the wall, not too near the pathway or it will reach out and poke people going by and you'll have to be out there policing it all the time. It's pretty and makes nice cut flowers so if you do have to break off a branch or two, take them in with you. The big stems will grow roots in a week, and you can add to the 'hedge' with cuttings as you go, too.
I'd envision sort of an espalier effect, where you prune off any branches growing towards the path or the wall and just let it grow sideways and up.
