Squarespace 7.0 - Site Header Logo

Go to the home page, then in configuration click site styles, and click your header, the options for the various parts of the header including navigation, title, and subtitle will show up in the panel on the left when you click a part, not on the page itself. If you are adding a logo instead of a title that is done in the design, the first setting is logo and title. You should also get a small black panel that says edit title when hovering over the title if you have one and a panel that says edit navigation when hovering over the bar. This is the way 7.0 usually works but could be a bit different depending on the template you want to edit. It would be helpful to let us know which one you are editing.