Hi.. welcome to FTR..

I'd sugguest you start with something that has "micro limits". Party poker has a soft/loose game but if your just trying to get your feet wet, a site with smaller limits might be a better fit for you.
My advice would be poker stars for 2 reasons.

Poker Stars has micro limts as low as .01/.02 NL and .02/.04 limit.
Poker Stars also has a better tourney format and lower rake on the $5 Sit and Go.