I'm not familiar with that skimmer but skimmers generally take 2-3 week's to break in. As far as where the bubbles should be, it's largely personal preference. Having the bubbles higher up is called wet skimming, which results in a lighter skimmate. Having the bubbles lower is called dry skimming and results in darker skimmate.
Personally, my skimmate varies. Sometimes I might wetskim if I feel like I'm feeding a lot or there's an abundance of organic carbon. If I feel the tank's running with minimal organic carbon and running fairly "œclean", I'll lower the bubbles and do a dryer skim.