Changing Links in Main Menu (Header)

I got editing permissions for the website atxcampuslions.org for the purpose of updating it. The links in the header of the front page of the website are from last year, and I want to update them to this years’ information. Whenever I’ve looked up how to do this, the forums say to go to Appearance -> Menus, etc. and change it from there. However, when I’m editing the site on http://atxcampuslions.org/wp-admin/, I don’t see the Appearance tab anywhere. Do I maybe not have the permissions to edit it? Is the tab simply somewhere else or labeled differently?

Thank you!

The page I need help with: [log in to see the link]