Click on the lock icon at the bottom of the screen and enter the password. It should then appear unlocked. If you don't unlock then any edits you make won't be saved.
There are a few things to know about using the federated wiki.
Select the wiki button at the bottom of the screen, next to pages, to enable or disable editing.
To edit a paragraph double click on it
To remove a paragraph just delete all of its text
Paragraphs can be dragged up and down to change their order, or moved between pages
To add a new paragraph use the + button
You can use left and right cursor keys to move through pages
To claim/fork a page from another server click on the flag icon
When done editing click on the wiki button again
Different versions of the same page on different servers are represented by boxes at the bottom right of the screen. You can double click on them to see the different versions, and use the flag icon to fork if you prefer that version