Learn how to use it from the documentation located at https://triplelog.com/writer/readme.html. To give you an idea of what is possible, that page was created with Triplelog Writer and is entirely javascript-free. The total network load is about 100 KB - most of which is the Katex CSS and fonts.
I think it is really easy to use, but the documentation is probably not good enough yet to make everyone agree with that statement. If you have any questions about how to use it, ask away.