The following are all the steps in order to install Playground to Grarrysmod. Start by having Garyysmod installed and ran once.
1. Go to your garrysmod/garrysmod/ folder and rename your addons folder to Addons1
2. Go to "link" and download Playground 3.0, open the .rar file
3. Merge the "Garrysmod" folder from the .rar file to your existing Garrysmod folder and copy and replace any existing files.
4. Run Garrysmod, Playground will load automatically as the default gamemode and can be changed at any time.