I need to fill in the background for a project I have been working on but whenever I try to fill it in it says area is not bounded cannot fill. If anyone could help me I would greater appreciate it.

Most likely, you`re using the bucket tool to apply color on an empty background. That would not work since that tool is meant for applying uniform fill on already created shapes. If you`d prefer to have plain color as a background either go for Document Properties (Shift+Ctrl+D) and change the background color - or - create a rectangle which is larger that the "page" and then choose the color for it.

The rectangle approach has some advantages since that way you`ll be able to apply gradients or similar effects, where the same is not possible trough the Doc Properties.