E commerce plugin on wordpress

I am new to wordpress and need some help with the integration of a shopping cart on my webpage.

I have products listed that when selected go into a getshopped gold shopping cart. All this works fine, but when trying to checkout using paypal as the gateway. I keep getting an error 404 page appearing.

I do not know how to resolve this. Any suggestions would be much appreciated.

The wordpress settings do not allow me to insert any details for my paypal account.

I really would appreciate any assistance someone can give me!

Thanking you in advance
T