I am not going to write up my own guide here, but I will link you to some of the many guides and utilities out there that will help you learn what the two types of content are and how to properly install them in your game.
Installing Custom Content (TS3):
Installing Custom Content (TS4):
Programs and Utilities (TS3):
Programs and Utilities (TS4):
Requirements for My Content:
Take special note people of TS4. I keep my game fully updated so it can be said that my content is only compatible with the latest version EA has released. If your game is not fully updated and you are wondering why content is not showing up, that is probably the reason why. Content is mostly not back-compatible because of the changes EA has made to some of the core coding since release (however, older content is mostly compatible with the newer versions except for some CAS content made for the sims 4 demo that has not been remade or updated).
You should also note that with the 64 bit patch, EA forces all cc to be turned off every time you update you game (this is mentioned in Carl's Guide above). You will need to turn on cc each time you update through the options menu. This requires you to restart the game for it to take effect.
My content is also always in a .zip or .rar file. These need to be extracted once downloaded. I mention it on every post, but I do still have people that don't read down that far. You need a program like WINZip or winRAR to extract the items from the archive before placing in your mods folder. They will not work if you leave the archive un-extracted.
Hopefully you find a solution here to installing my content, and content by others, so please read through this before asking me questions. It is often a simple solution for most people. But if problems persist, please post in the related post or contact me and be as specific as possible because saying "your content isn't working in my game" does not help me help you to track down the issue.