Ebay and paypal question! please help :)

Hey all

Im buying something using paypal from ebay, its a set of maths textbook kinda thingies. I know how to pay with paypal so thats okay. The total comes up to about £10 which is fine. However the seller hasnt got an item listed, but i contacted them and they said if i wanted it, that i should add an additional £5 to my total paying fee.

I dont mind adding the £5. But i dont know how to!!

So basically, how do i send more money than the total of the product and delivery listed??

Sorry if that sounds confusing!

Thanks