So...there is dirt at ground level now?
You will need footings that go below the frost line and a qualified builder/contractor to make the installation. You haven't offered enough information to know what comes next. I assume this floor will be elevated over more crawl space?
A licensed plumber and electrician is also in order.
If your intention is to DIY this project then make a small drawing with relevant facts of size and elevations and take it to your local building inspection department. They can tell you what you can and can't do and they would be happy to sell you the required permit(s).