Hi Kashahime !
You'll need to use CSS to change the font size.
First, open the file
style/main.css. Then, find a rule that looks like this :
Inside braces, add
font-size: yourSize; where yourSize can be
1.20em (em is a special unit that tells in this example "my text should be 20% larger than its original size")
finally, it might look like this :
font-size: 1.3em; /* 30% larger than it's original size */
don't hesitate to reply if you need any more help !