Un-updatable Sims 3 and how to "manually patch"

Hi,

First off I am new to downloading games through these means and am very ignorant to the terminology being used so please be as specific as possible when responding so I can understand.

I downloaded everything properly (converted to .dmg files using disk utility) but when I go to install the expansion packs I get a notification saying that the version I have of the Sims 3 is not updatable and I can't install World Adventures on it. When I open the game it says I have an unauthorized copy; I'm not sure if that information is useful but I'm adding it anyway. I tried another random expansion pack just to see if I was able to install it and I was not. I have seen some people being told to "manually patch" but I don't understand what that means nor do I understand how to install the ultimate fix on a Mac. I need a step by step explanation (what to download and where to put it, etc.). All I see is links that I don't know what to do with or where to put but not a detailed guide for someone with no previous understanding/experience.

Also, I have already looked at the updated Sims 3 installation guide but it does not work for me because I cannot get through the step about downloading expansion packs. 

I apologize for my ignorance but if anyone could help me then I would really appreciate it. Thanks.