You don't need to make one since you already have one. When you buy or install through Origin, one is created for you.
Try logging in with the same info that you use on Origin and then go here to add Dragon Valley to your account: https://store.thesims3.com/myAccount.html
I have the same issue but i downloaded the game through steam. I am doing everything i can to make my account but it says i already have one when i don't think i do. And i would really like to download items from the store place thing to add to my character, i clicked i forgot my password and it says it sent an email but it didn't. I have a gmail.
