There are so many ways of doing it that it's hard to give specific advice. Maybe you should start playing live as a group and recording things as separately as possible. You should be able to record up to four tracks at a time, you just need to figure out how to get things into the recorder and assigned to appropriate tracks. What is your jam space setup like? For example, what do people play and sing through?
Here's a live recording setup: Add a small mixer and some mics to get the drums into one channel and record on track 1. Then get a line out from the bass amp and hook it to channel 2 going into track 2. Put a mic on the guitar amp and put it into channel/track 3. Connect the PA with the vocal(s) to channel/track 4. Set levels, press record and jam. Mix down to stereo and record your output on your computer. If you have more than one guitar use the mixer you got for the drums, pan the drums left and the guitars right to submix each group into a single channel/track.
For a more sophisticated process, track separately. Connect four drum mics directly to the recorder. Note that it has 1/4" mic/line inputs, so you have to have cables and mics that work with them. Record the drum part on the first four tracks. Next record bass, guitar and voice one at a time on the other four tracks. This give you the option of retracking parts if you make a mistake, and it allows more control over the mix.
You may find the additional small mixer handy for submixing more mics than the 280 can take on its own, or for other uses. For example, say you want to record the drums, but you want to have the bass/guitar/vocals playing along live for the drummer's reference. Send a monitor mix of the drums from the recorder to the extra mixer and add bass/guitar/vocal to make a headphone mix for the drummer. He hears the whole band but you just record the drums.
Another technique is to record the whole band playing live just as a scratch track. Then you record the drums while the drummer plays along to the scratch track. Once that's done you can go over the scratch track with another instrument. Scratch tracks can be a single track with everything on it or split onto separate tracks so you can give the drummer some control over his monitor mix.