I Need Help!

Ok everyone, I'm still not very savvy with this whole blogging thing. So I can't figure out how to make my titles bigger! For some reason it won't let me change the font or the size of the title, but it will let me do that for my paragraphs. I'm sure you all could help me with this since you're much better at blogging than me. So if you know, than please tell me! I've been trying to figure this out since the very beginning and just haven't been able to so I decided to finally ask all of you. :) Please help me out if you can! Thanks!