Pull in lever, move shift pedal, remove hand from lever, let go of pedal. These bikes are odd as you don't just click it into gear - you have to let go of the clutch lever first or sometimes it misses the gear.
As far as what gear at what speed, it depends entirely on load. You don't want to lug the engine down, but conversely these have a lot of torque in the LOW RPMS, not high-up. First gear really is only for getting off of from a start, and Fifth gear is really only for top-speed cruising. Anything in-between is your choice.