For some the Bassline machine might look a bit confusing since it doesn't have a pattern editor (yet? :).
The trick to get longer lengths than a 16th note is to use the slide feature. A slide on a note basically connects the note adjacent(to the left) to the note with the slide trigger (on the right).
So to get a 1/4 note, you would select 4 16th notes in succession. Select slide for the last three, then adjust accent and up/down for each of the notes. This will give the 303 wah wah effect and also give you longer notes.
Using this technique along with filter and envelope changes, the Bassline machine can sound very convincing.