In order to edit this wiki, you need to log-in first. The button is in the upper right corner of the page. Simply use your normal ZHdK credentials, that is, the ZHdK user name and password you also use for email and WLAN.
Once your logged in, you go to the page you want to edit. If it has more than one section, go to the section you want to edit and click the edit button. The button is always below the section you want to edit.
Then, you are in the edit mode and change the text, add material and format it, using the tool bar above the edit field. Once you're done, you need to save the changes and thus leave the edit mode. Don't worry, if you see a mistake, simply change back to the edit mode and correct it.
If you need more help with formatting, see this section of the DokuWiki manual.