FOR VERSION 3.0.9 OR EARLIER ONLY
Here are the steps to add webfonts from Google webfonts.
1. Go to Google Webfonts
2. Select some fonts you wish to add. In this example we add 'Roboto'.
3. Choose the weights you need and copy your Embed code.
4. Please leave this site open as you need the fontweights later.
5. In your Wordpress Dashboard on the left side click on 'Custom Fontsets -> Add New'
6. Choose 'Webservice' as the Fontset Type.
7. In the 'Embed Code' textarea please paste the embed code you copied in step 3
(Note: Always copy the full code with the < script > or < link > tags, not just the link)
8. Now fill in the weights. For the Google Webfonts, this is pretty straight forward. In this Example we use 'Roboto' in the weights: 'light', 'regular', 'semibold' and 'bold', Always have in mind that not every font got the same css weight for light, semibold etc. In this case 'semibold' hast the css weight '500'. Normally it has '600'.