[FAQ] Invalid and Used Serial Codes & Games not showing up in Origin

Ive actually brought the disc of the sims 3 and some of the other expansion packs, i had to install origin to be able to install my game, which i did then when i entered my product code with origin it said that it couldnt be redeemed on this site and sent me to the sims 3 website so i made an account and registered my game there and i still cannot install my game, i have been googling for hours for what to do, nothing has helped me, i did not waste $120 today, all i want to do is play my sims game. Why does this have to be so hard?!?!?!