The standard way to create a track is to add percussion instruments to the Beat+Bassline Editor and instruments for melody tracks into the Song Editor. Then create different percussion loops using the Add bassline button in the Beat+Bassline Editor for each rhythmic element you want - a main bass line, a hihat line, special rhythms and breaks, etc. These are listed in the Song Editor as they're created. To make them play, click on the start bar in the track's timeline to create a new block element (segment). You can also drag in Beat+Bassline blocks to make the pattern go across multiple bars. The same technique can be used for repetitive bass lines, if you create them in the Beat+Bassline Editor.