You're almost done with the setup. The last thing is to choose username and password using which you'll login to the application. This password is also used for generating encryption key which encrypts protected notes.
This setup needs to be initiated from the desktop instance, please open it, go to settings in the top right, click on sync tab and then click on Setup sync with server instance.
Please enter Trilium server address and credentials below. This will download the whole Trilium document from server and setup sync to it. Depending on the document size and your connection speed, this may take a while.