As always when working with your template and HTML, I strongly suggest you back up your template before you make any changes.
The font should be fairly easy to change on any template. If you go to Layout > Edit HTML > search for font, you should find some code that looks like this:
<Variable name="bodyFont" description="Text Font"
default="normal normal 100% Georgia, Times New Roman,Sans-Serif;" value="normal normal 100% Georgia, Times New Roman,Sans-Serif;">
The code will vary depending on your template, but it will look similar.
The parts you need to pay attention to are the parts in bold in the example above. Notice that they match. Georgia, Times New Roman, and Sans-Serif are types of fonts. By listing them in order, the code is telling your browser to display the text in Georgia. If that’s not available, display the text in Times New Roman. If that’s not available, display the text in any sans-serif font.The browser just goes down the list until it finds something that works.
You can change this information, and thus the font displayed on your blog, by changing the name to the font you’d like to use (make sure you change both places–see bold in code above).
Preview your changes and see how you like it. If you don’t, you can always revert back to the original because you backed up your template before you started. Right?