How do I enlarge the text on my fanfiction.net stories?

I know, it's a lame question, but for the life of me I can't figure it out. I even downloaded the recommended program which is supposed to carry over format changes, and it does things like bold, italic, and underline, but that's it. I've seen other peoples stories with larger text so I know it's possible. Mine looks about 10 point font right now, and it's hard to read, hence wanting to fix it. Thank you for any help. Ja ne.