The site is a separate site from Ten-Tenths and you'll need a different login if you want to contribute to it. There is a
Log in / create account link at the top right of each page, you can use this to create a login.
Once you've logged in you'll see an "Edit" tag on every page, you can use this to edit the page you're looking at. Don't worry if you edit and it goes totally wrong changes can be reverted.