Save files. Make copies?

With members help I have managed to create a design for a bench and table. Really two questions. How can I save my original bench design while also using the original to try some modifications. I designed the bench and table separately. How can I bring them together in a single presentation?

You can use Save As to create a new file with a different name and then make modifications to it to make a new version.

Import one of them into the other.

Thank you. Very helpful.