well l have 4 dollers in my pay pal account but l have no credit card and the thing l want ot buy is 1$ but it askes me for my credit card why do l need to enter it if l have 4 dollers already in my paypal account?

its just a funding source that all it is
when you send the money it will first take from the paypal account
if there is money there as well as give you other choices
like echeck, instant transfer from your credit card or checking or saving account what ever is your primary funding account for paypal)