Sims 3 Supernatural won't install

[akiresenpai]

I have sims 3 on steam and sims 3 supernatural cd and it wont let me install sims 3 supernatural. It says I need a copy of sims 3 or need sims 3 to install it.

[MrsFlynn]

I've never come up against this problem, but in my search on the problem. I've found this to try:

Sims 3 Expansion packs won't install
http://answers.ea.com/t5/The-Sims-3/Sims-3-Expansion-packs-won-t-install/td-p/2560304/page/1
-- Go to post 8, it has some tips to try.