In sims 3 you don't buy clothes! You can just click on the dresser and choose desing outfit (or something like that... I don't have the english edition so I don't know the exact command!) And once you're there, you can design 3 different outfits for each category~ And if you click on your sim you can change the outfit he's wearing!
Your question is quite ambiguious, so I'll give you two answers. 1) In the game, you can't buy clothes anymore. You buy a dresser, click and select "Plan outfit" and then you can create new outfits for them (you can have a max. of 3 for each catagory) 2) You register your game at thesims3.com, redeem your Simpoints, and buy clothing from the store. (or you can google "free Sims 3 clothing download" and get some clothes from there, but i prefer the official Sims 3 store)
Buy a closet then click on it and it will say change outfit and soomething else under so click on the thing under then u can change the outfit and add outfits and everything
