When designing, it’s important to choose wisely with fonts. If your design is going to be out and about in the world and you’re using a font that’s not 100% free, you get into trouble!
For instance, if you’re creating an ad for someone else, you shouldn’t use fonts that are only “Free for personal use”.
Dafont.com is a great resource to use to find 100% free fonts. All you have to do is download them and add them to your fonts in order to use! Make sure you save the font in a place that you can go back to it just in case! However, just because a font is 100% free doesn’t mean that it’s able to be used for commercial. Be sure to read the details of if you need a certain license to use a font or not.
If you have questions about how you can use a font, you should talk to the actual developer!