I'm assuming you have the E420D oa model since you stated it was a smart TV and 42 inches.
Adding a New App to the VIA Dock
Though your TV arrives pre-loaded with featured VIA Apps, new
Apps are continually being added to the Widget Gallery. The VIA
Dock can hold a total of 17 Apps.
To add a new App:
1. Press the V Button on the remote.
2. Highlight the Connected TV Store App by scrolling left and
right using the Left/Right Arrow buttons on the remote. (The
highlighted App is in the lower left corner of the screen.)
3. Select Connected TV Store by pressing the OK button. The
Yahoo! Widget Gallery is displayed.
4. Use the Arrow and OK buttons to select a new App.
5. Highlight Add Widget to My Profile and press OK.
Removing an App from the VIA Dock
To remove an App:
2. Highlight the App you want to delete by scrolling left and
3. Press the Yellow VIA Shortcut button.
4. Highlight Delete Snippet and press OK. The TV displays, "Are
you sure you want to delete this snippet?"
5. Highlight Yes, delete and press OK.
If that doesn't match your model number we will need it to research the procedure. I would expect that should be how all Vizio App based units function. They're pretty consistent across the board.
If that doesn't work, get me your model number on the back of your TV set.