In the upper box, enter some words that fit your desired aesthetic. Hit "Generate" to get a bunch of new words in the lower box.
At first, you'll mostly get garbage. Pick out the words that look okay and append them to the text in the upper box. As you enter more words, the quality of the output will improve.
Make sure your input words represent the entire alphabet you want to use. If your input text doesn't have any "e"s in it, you'll never get any in the output.
The input is alphabetized and de-duplicated every time you click "Generate", so you'll have a ready-made wordlist. If your output lacks variety, go through your input and weed out similar-looking words.
It's possible to train a good generator just by copy-pasting good output words back into the input. However, you'll get better results faster if you use the output words just as inspiration for what you type into the input.
Don't shy away from including very short words in your input. They seem to improve output quality.