The Administration Email address does not appear in your shop. This email is the address where order confirmations are sent when someone purchases something from your shop. It will also receive notifications concerning stock quantities if you choose to have the shop monitor such things (explained further down the page).
The Currency Selection is simply the sign the shop will put before a price. Most people will leave this as $.
The Default Country Selection dictates which country is preselected on the checkout drop down for your customers. If your shop is based in the United States but the majority of your sales are to the United Kingdom, you may choose to select 'United Kingdom'.