adding an American address to a UK account, is it possible?

[123jase]

I am visiting America soon for a holiday and have found a service that will hold parcels for me until I arrive. How can I add their address to my account? I would like to take advantage of the better deals in stores over there.

Thanks

[123jase]

I dont want to open a US pypal account as all my cards are registered in the UK and this would cause even more problems.