Is the Edit tab missing, or are you trying to change the default text? The default text will always appear if the Edit tab is left empty. If you want different text, fill in the Edit tab.
On the other hand, if you want different default text, these are phrases in your forum's language system. Do a phrase search for some of the words you see in order to find them and edit them. Each kind of page (there are quite a few) uses different default text.