How do I adjust the font size?
To adjust the font size for the whole document, you can set a global option in the documentclass - see e.g. https://www.writelatex.com/read/kjbnzqbvqhvr
The default article class is limited to 12pt, but you can go up to 14, 17 or 20 points if you use the extarticle class, e.g.:
For details, please see http://www.ctan.org/tex-archive/macros/latex/contrib/extsizes
To change the size of the font within the text you can use commands such as \large - see this blog post on texblog.org for more details and examples.