Using a Midi to template time signature and then record instruments vocals

Ive started a song by opening a midi file to import time signature and a backing track to practice against.

However I'm unable to add normal tracks for guitar and vocals once I've done this, selecting input of chaels from the interface is not available, rather than the standard input choice of 1 to 8 i instead have the options of input L or input R

it seems importing the midi changes the configuration of how the interface is being used / accessed by the DAW, and I ain't got a clue how to fix this. I'm sure its very simple but I cant find what i'm doing wrong / what step i'm omitting.

TIA