Micro Dot Phat

After a bit of help, might be a really newb question but im no python programmer here, just a lowly user tinkering. ive got the micro dot phat, its happily setup with node red triggering some text files, what i would like though is the ability to display text from a mqtt topic. After a couple hours googling i have drawn a blank, probably not surprising as i dont know how to phrase it. Hopeing someone can advise or throw me a link
what i want is to subscribe using node red then have the mqtt string shown on the phat, i.e. temps/pi gives 42 and thats popped on screen.
i could even capture the mqtt to a file in node red then display that i just dont know how to show any external text/file in the display.