Sims and Lots for The Sims 4™ contain several files that are usually zipped in a compressed folder usually in the file format of a .zip file.
The files of the creation need to be placed in The Sims 4™ Tray
folder where the game can access the files and make it available in your Gallery in The Sims 4™ game.
The Tray Folder can be found in this folder on your Windows PC:
Documents/Electronic Arts/The Sims 4/Tray
After following the links and downloading my Sim or Lot creation from my MediaFire, you will find a .zip file in the default area where your downloads go for you and your PC.
You must then unzip the file and place the contents of the download .zip file into your The Sims 4™ Tray Folder.
Launch the game and you will find the Sims or Lots in your Gallery Section in the game.