To install Simple Grids & Tables, unzip the zip file and place the system/user/addons/simple_grids folder from the zip file into your /system/user/addons folder, and the themes/user/simple_grids folder into your themes/user folder. Login to the Control Panel and go to Developer > Add-ons and install Simple Grids & Tables. Once installed you will see a Simple Grid and Simple Table fieldtype available when creating a new custom field.