Modifying fonts within a theme

Hello! Pretty new to WordPress and website development. Wanted to get a site up and running so purchased a hosting package, installed WordPress, purchased a Theme and have that installed, and have uploaded some content….all looking good so far!

I’d like to modify the fonts that are used throughout the theme, and whilst the theme has good customisation options, it doesn’t directly have any options to play with the fonts.

There is however a section in the config window to add ‘Additional CSS styles’. I wrote to the theme developer about how to modify the menu font and he gave me some code to put in the ‘Additional CSS styles’ box as follows:

#menu ul li a{
font-family: “handwriting-dakota”, “geneva”, sans-serif; text-transform:none;font-size:13pt;
}

That’s fine and has done what I wanted. But I actually want to extend this now so that I can individually modify the font sizes, style etc. of all the elements in the site (headings, body text etc.) How do I extend this code to do that? Is there somewhere on www.remarpro.com I can read up on how to do this CSS style code?

Also one other question, I’ve noticed that whilst the above code works fine on my mac, it doesn’t work on my Windows PC presumably because the font isn’t there. How do you deal with different machines having different fonts?

Appreciate any help! Many thanks……Rob.