Font Size in Inkzine

The font on my website trekkinggreen.com is quite small and difficult to read. I would like to change the font size, but do not see this option under Appearance-> Theme Settings. I could go through and change each post and page individually from paragraph to a Heading to make it larger, but it seems like there should be some way to just change the font size. I am not a coder, so if the problem is something I will need to change in the code I will need very detailed instructions.

Thanks for your help,
Amy