Are you looking to record them all at the same time, or one at a time?
With the interface you have, you can record 2 things at a time: 1 instrument and 1 microphone.
So, if you wanted to record guitar, piano and mic at the same time, you could record them all into one track using the mic, or into two tracks separating the mic’ed instruments on one track, and a DI’ed instrument into the other track.
But I wouldn’t, generally, recommend combine the recording instruments onto a single track this way, as you will no longer have the ability to mix them.
If you want to record 3 instruments simultaneously (counting the mic as an instrument) you will need an audio interface with at least 3 inputs.
If you want to record them separately and mix them, you can do this as much as you want, with as many tracks as your DAW version supports and your PC can handle. In some cases this is, effectively, unlimited.
As to how you do this depend on what instruments you have. For instance, for the guitar you might have:
- A guitar with no pickup that you record using a mic
- A guitar with a pickup that you record DI into the audio interface
- A guitar with a pickup and an amp that you record with a mic
- A guitar with a pickup and an amp that you record DI from a line out on the amp
- A guitar with a pickup and an amp with USB that you record directly to the PC
For piano, if it’s an electronic piano, you may be able to DI this into the audio interface or, potentially, connect it via a MIDI connection (typically over USB) and record the MIDI, and use a virtual instrument on the DAW.
You will, however, need to physically swap the interfaces over depending on what you are recording. If you don’t want to do this then, again, you’ll need a new audio interface with more inputs.
Cheers,
Keith