I have been using AnyFont for quite a number of years. It’s a nice little app to install fonts you have licensed. I believe it was one of the first, if not the first, apps to let you manage your iOS fonts.
In addition you can purchase, for a small amount, a font bundle. I haven’t done this myself so far, since I’m not interested in these fonts, but maybe I should (to give the developers a bit of extra money).
When installing fonts you have to click quite a few times, but simply follow the instructions. They’re straightforward.