To get write access to FreeSurferWiki you need to email fswiki-help <fswiki DASH help AT nmr DOT mgh DOT harvard DOT edu> and request an account. We will create one for you and you will receive confirmation that you have been added to the Wiki users list. You can then login to the Wiki by going to UserPreferences.
NOTE: Always login and edit pages using the https url (not http), as the https url bypasses the page accelerator that is running (which doesnt play nicely with logins and edits).
Please feel free to email fswiki-help <fswiki DASH help AT nmr DOT mgh DOT harvard DOT edu> if you have any questions or encounter any difficulties.