If your card starts with 10000/98260 and has a 4-digit security PIN then you can use it online or in-store. It doesn't matter if it is an eGift Card or physical Gift Card.
At Checkout choose 'Gift Cards' as your payment option and you'll be able to pay either part or the full amount this way. If your card doesn't have a 4-digit PIN then you'll only be able to use it in-store.