Ya it seems your confused on the process of What is a Virtual Instrument.
We load a virtual instrument into the Channel Rack to play MIDI Notes.
Most often we use one Virtual Instrument per pattern.
So load one virtual instrument for your piano, and add your MIDI Notes.
Then load a new virtual instrument (so you have two different virtual instruments loaded), then go to Pattern 2, and then play MIDI Notes in that new virtual instrument (your guitar).
If you want to hear both patterns, you want to be in Song Mode and both patterns should be in the Playlist.
If you just play in Pattern Mode, you’ll only hear back that one pattern.
If you choose to make all melodies and sounds in one pattern, you will then have to break it apart and use split by channel, or cut/paste those sounds into a new pattern later on so you can have full control of your arrangement.
If you’re really struggling and just can’t understand it, you can always book a lesson.. many students most often just need 1 or 2, then the courses are enough so they can keep learning better on their own!