I’m also using a PreSonus. I suggest you read through this, as it has been carefully written:
I found this video helpful as well:
In short, you should use one of Rack’s callibration modules (I can recommend Expert Sleepers’ Voice Controller, very easy to use) to “tune” your interface. Since mine is USB-powered, the output is very low voltage. So I use an external amplifier module to adjust it to wanted levels. It’s a bit cumbersome, but works.