How do i change messenger font size? its too small. all other yahoo fonts are large?

when i go online on my phone all of the fonts are large. when i get into messenger and try to view my messages the font is so small i cant see it. i have changed all the fonts on my phone and on yahoo and cant seem to change the size once inside messenger. if this makes any sence. i can change the color and everything else just not the font. what can i do?How do i change messenger font size? its too small. all other yahoo fonts are large?
does your phone Messenger have a preferences tab?

if not,

do you know how to change font size in computer based Messenger?

can you set up Messenger in your computer then tell your phone to synchronise?

alternatively, it may be possible to access your phone Messenger account from your computer and alter the font. the phone will automatically adjust.