how are you meant to wungle it

Wat do you mean? How are you meant to wungle the text? Just click on the extension in the extensions list on mobile or under the puzzle piece on desktop (you can even pin it for easier access) and then type in text to be wungled.

Finally after clicking or tapping the wungle button just paste what was copied to your keyboard at the start of a paragraph in a tumblr post. That pasting should look like it did nothing until you look at the post outside the editor and click the wungle text button on it.

Or did I misunderstand your question?