My text is too small in Invision

Hello,
I'm new & attempting to set up a forum using the Invision layout.
The text in the message boxes is very small in the default setting - this thread would appear to address my particular problem:
https://help.forumotion.com/t99638-how-to-change-polices-and-size-of-text?highlight=bigger+text.

However could someone explain to me where in the Admin panel do I go to input this text - sorry to sound so dumb but I'm completely new to all this - I have searched the FAQ section but can't see anything obvious.

Administration Panel>>Display>>Colors & Pictures>>Colors

Colors Tab

Thankyou so much!
It's simple when you know how

Glad that I could help.