Downloading autoCAD

autoCAD is giving me two options; either to install or download. which one do i do?

You can really do either.
Install is for a single computer. Download is for single or multiple computers.

Thank you!
When i try to save it in an older version, i dont see the options button. what do i do?

When you select ‘save as’ you should see on the bottom of the dialog it say ‘file of type’
Select there an older version