All fields are optional except for your E2 Username, and E2 URL. You must use your real E2 username or you will not be able to retrieve your password.
Once you have registered, your password will be sent to you via private /msg on E2. This is done to ensure that only E2 members can register for the site.
While all parts of your "location" are optional, you must enter at least your country if you want to be included on the E2 Globe.
NOTE: While your street address will never be displayed publicly on the site as text, it will be used to more accurately show your location on the E2 Globe. If you wish to be displayed more accurately on the map, but do not want to give your full address, you could just put in the street name (or even a street down the block from you). With no street address, you will be displayed in the middle of the city you enter.