how to edit the links in the header

I am trying to edit the header of my site in squarespace (I am in the trial period, don't know if that takes away the ability to do some stuff?). There are three link-titles in the top left of the header (they came in with the original template) - "services" "about" and "contact". When I click to edit the header I can change the colors, the logo, insert one completely unmovable button at the top right (!), but there is NOTHING to access in order to neither change the text of the three above mentioned links, or to activate them as functioning links. I have searched high and low to find some way to do this. This is a basic function in any website, so making it work and editing the text of these links should be readily available. Where is it? I need help. If I can't get passed this I will have to give up on Squarespace....

The password to see the site should be 67impala, but when I enter it and click save, the page fills in the password section with some 17 position password which I can't see... Great.