how do i remove uninstalled Mojave software from my computer

One can not Remove / Uninstall Mojave if the Mojave was installed.

The Operating System Mojave 10.14 can only be " Removed / Uninstalled " by downgrading to a previous Qualifying version of macOS. This is achieved reformatting the Entire Drive.

Then, re-installing the previous Qualifying version of macOS via several methods including from a USB Bootable Installer, Internet Recovery Mode and / or from a Time Machine Backup that contains the Previous working version of macOS.

If, as you say, the uninstalled Mojave has been downloaded, its DMG file should reside in your Applications folder. (Or in your Downloads folder.) Simply right click on it to move the file to the Trash and then empty it.