I'm a 'chuck the manual and dig in' kinda guy, but this thing is virtually indecipherable without it.
You may even struggle with that because it seems to be translated poorly from Japanese.
Select 'style mode'. Go through the entire style library and make a note of which ones you find usable.
Each style has an Intro. A part, B part, transitions for A & B, and an ending.
Think in terms of 'what can I add or take away from this to apply to a new idea?' Use the MIX feature to alter the levels of the parts, or the MUTE feature to mute them from the style track.
Save the style or 'groove' to a user slot for editing. Add parts by recording and quantizing them if necessary. Use the 'step' feature to delete instrument parts. I use my left thumbnail on the DEL key while stepping through the sequence with the stylus in my right hand.
Although the sounds are a little outdated, it's a viable songwriting tool in that all the rhythm parts are there (drums, bass, acc1, acc2), and 4 more tracks which can be added in song mode after rhythm editing.
Get creative with the FX, especially the pan delay, as you can bounce rhythms to create some pretty cool stereo grooves.
Dig it for what it is - a cheap tool you can use on a plane to make music which you can later convert to more contemporary instruments via MIDI.