Here's how you can add the Workspace Switcher applet to the panel on your Linux Mint 13 Cinnamon desktop.
1. Click the Settings Applet on the panel.
2. Click Add or Remove Applets.
3. The Cinnamon Settings menu for applets will appear.
4. Scroll down to the Workspace Switcher applet, and click the checkbox next to it.
5. You'll see workspaces appear on your panel, you can switch between by clicking on the workspace you want to use.