To add backgrounds to your project click on the Backgrounds tab located on the left-hand side of the Toonly interface.

From there, select the background you would like to include in the project and drag and drop it into the project area.

If you would like to replace the current background, simply drag another background into the project area to replace it.

Drag the solid background (in white) into your canvas from the backgrounds tab.

Then, in your timeline at the bottom, right-click to open the color selection menu and choose the solid color that you would like to use in your project.