I think you're already editing your spec, because the designer is open. Under maintenance...specifications, there's an open button adjacent to each spec. The 'Edit' button doesn't apply to this page, that's why it's greyed out.

If you want to insert some text, make sure that the appropriate Toolbar is visible. View...Toolbars...Standard Components. Insert a 'label'.

From that point forward, it will get more difficult.