Due to constant spamming, a password is now required to edit pages on this wiki. The password is the first (given) name of the guy who wrote the PICK database, and also a description of the spammers who make this a requirement :-)
Login to Preferences (link at the top and bottom of every screen), enter your name or nick name, and put the secret password in the "Admin Password" box.
If you login as an editor, at the bottom of every page is a link "Edit text of this page". Click on the link and the text of the page will be shown in a textbox. Make whatever changes you like, and click on "Save". After logging in using preferences, your name will be listed as the author of the page/change.
See HintsAndTips for some basic formatting commands.