If you don't see the option to allow access to your camera and microphone on the first set up screen, (see image 1 below) this is usually because you are using "Private Browsing". This is called a 'Private Window' (Firefox), 'Incognito Window' (Chrome), 'Private Browsing' (Safari) or 'InPrivate Browser' (Internet Explorer).
To complete the interview, open a normal browser window and log in again with your email and password you've just created. You should now see the dialog box shown in image 2, select the 'Allow' and 'Remember' options to allow access to your camera and microphone.
image 1. (Using Private Browsing)
image 2. (Using Normal Browsing)