Backup origin change

I have mistakenly backed up my C drive but wanted to back up D drive. Could anyone suggest how can I change the origin drive?

Many thanks

How did you perform your backup? What is the name of the application governing your computer’s backup behavior?

Dear Trancer,
Thank you for your reply. I have performed backup by the software that came with the wd passport ultra (WD Smartware). Please let me know that is what you are asking.

Many thanks