Intsalling a cracked EP to real game

Hello!
I apologize in advance if I'm posting to a wrong sub-forum or anything.The thing is, I have a store bough,legal version of The Sims 3.Now, I really want Late Night but I currently don't have the money to buy it. I've read the threads on this forum regarding the issue and really didn't understand a word you guys were saying. I don't get if I need to apply the crack to my legal, base game? I'm worried it'll mess up my game.I feel dense.   

If any kind soul could explain the process how-to I would be very grateful.
Thanks in advance!

The way I did it was to download it via katproxy.com. Then you should get a .rar type file... Use WinRAR to extract it to Electronic Arts/The Sims 3/ Downloads (on your PC file Explorer) then you should get an ICO file of Late Night with The Sims 3 plumbob thing and should also get the setup file along with it. Double click setup file and install it using installshieldwizard  Hope I'm clear!

I'm in the exact same boat. I also have a thread and have received some help although I am still confused. Nevertheless, the stuff said in my thread may help you.

Sims3Waffle wrote:The way I did it was to download it via katproxy.com. Then you should get a .rar type file... Use WinRAR to extract it to Electronic Arts/The Sims 3/ Downloads (on your PC file Explorer) then you should get an ICO file of Late Night with The Sims 3 plumbob thing and should also get the setup file along with it. Double click setup file and install it using installshieldwizard  Hope I'm clear!

I kind of get it,but I don't get why I should put it in my Downloads folder and the whole crack your game, no cd crack thing. Oh,well.

Solved my issue/concern!
I basically blindly followed the instructions in the *MUST READ* How to install Sims 3 correctly link (which I'm unable to link)
I explained everything I did in detail on Declan's thread if anyone's interested.I apologize for not trying before I question but that's me, paranoid all the time.

To the admins, you can close the thread!