Fonts are installed at a system level. Provided that they are installed properly, and are well-written, PrE will see them, when you start Titler.
To create a Style, just add an existing Style to your Text. If you want to do one with, say a Stroke and Fill, choose one from the Styles Library. Then, you can adjust all aspects of that to suit, say Font, Size, Stroke and Fill. When done, just Save that Style to the Library, and name it appropriately. Then, it will be available to you, for other Titles.
You can also use the Duplicate function, to base a New Title on an existing one, and just alter the Text to suit. Remember to do the Duplicate, as if you just change the Text in an existing Title, then every Instance of that Title will be affected by the change.