Game Help Talk:Downloading and Installing Custom Content

I followed all the instructions to download the "OMGWTFBBQ" but every time I double click on the package it opens up the installer and says something like: double click on an item you want to install. I tried double clicking it while the message was open but it just opens it up again. Does someone know what I should do??? This is by the way the first time I download something for the sims 2