There's more to it, but I've seen people get intimidated by all the buttons alone. This should simplify the main logic of the PO-33 interface as well as that of all the other pocket operators, which I've written more about here.
- The function of all those numbered buttons changes depending on what you hold down
- You can either record stuff by holding record and playing live, or by tapping record so the icon appears and then tapping the numbered buttons to place a sound. It'll place whatever sound you selected last (by holding sound and pressing a numbered button)
- You can layer a maximum of four sounds total on each step.
If you're way beyond this, here's the most comprehensive guide I've found for the PO-33, and another one for the PO-35 Speak (with some "secret" tricks)