How to calculate backfill around a foundation

Hello,

I'm new to this product and forum, but I can't seem to find any resources that explain how to go about calculating cut/fill when you have a foundation to work around. So far, I have done the following:

1. Defined existing conditions of site with outlines and contours.
2. Created a separate phase and used the platform element to drop grade around existing foundation that will be demolished.
3. Created a separate phase and used the platform element to drop grade around proposed new foundation.

From here I am stuck. I need to backfill around the proposed new foundation and add final grades, but I cannot figure out how to do this. If anyone has a procedure or suggestion for how to move forward it would be greatly appreciated as there seems to be nothing out there that explains what to do from here.

Thank you,
DM