That is why I recommended to make a backup first.
It is a little intimidating.
But if you open each css property and see a font size. Change it to something else. Then select the update preview area button.
For example:
.breadcrumbs
has
font-size: 9pt
Change it to say 20pt then click on the update button and you will see a change.
It is not something that is very simple.
Because first you have to figure out what css property is used for what.
There is some hint if you click on the ? next to each one but it is not completely intuitive.
