In the url-field on the top left you can enter a url in order to access another website. Press "Go" on the bottom right to access the website. A keyboard appears. By pressing the "@123" button on the bottom left you will get access to the number pad of your keyboard. Go back to the letter pad by pressing the "ABC" button on the bottom left. The "Cancel" button takes you back to your portal page.
Note that you can also switch between functions/keys by pressing the grey buttons. Find a screenshot of the keyboard below: