All floors and walls done on this site are packages. To install in the game unzip the files, Place the resulting packages in a folder in the "My Documents/EA Games/The Sims2 Folder". The folder can be the Downloads folder, a sub-folder that you create in the Downloads folder, or a sub-folder of the Sims2 folder.
Also Note: All Walls and Floors are displayed at 75% size. They were originally converted from Sims1 wallpapers which were at 50% size, so some blurring in quality is inevitable. However, I have managed to improve the quality of the image somewhat.