Questions About The New Ultimate Fix Installation Process.

I've read over the instructions, but don't fully understand them. It says that we only need to extract one .RAR file, if that is the case then why was all five .RAR's needed to be downloaded? Anyways, that's not my question. My question is; I've extracted part 1 .RAR into my Sims 4 files. Is that all I need to do or do I need to go through all 5 .RAR's and replace the files?

You only need to extract 1 RAR but you need to download all 5 parts.

After extracting you'll have a new folder with 13 subfolders and 1 installation guide. Copy ALL 13 subfolders and put them on your sims 4 directory.