You can request access to the CMS online. Simply choose the path of the website you need to access or write it into the note if it doesn't exist yet.

You must also write an email to zedv@physik.fu-berlin.de with the owner of the page you want to edit, e.g. the group leader in case of a group page, as a CC as a separate notification, unless you are the owner of the page in question.

You can find documentation on the CMS at Ex-CEDIS (unfortunately only in German). It also helps to look at the other pages of the Physics deparment. The ag-beispiel page has a couple of examples.