This is your main page. You can edit it while logged in by clicking on the Edit tab above.
To add additional pages, go to Content management > Create content > Page. Under the new page's Menu Settings, give it a Menu link title, and ensure the Parent item is set to Plant Physiology & Biochemistry Lab under <Faculty Navigation> in the drop down list.
This page's web address is determined by the title of the page. For example, if you changed the page's title to "Cute Kittens Lab," the address would change to be http://biology.unt.edu/cute-kittens-lab. You're free to change the title as you see fit.