Flying wings usually have the CG somewhere in the range of 10-15% of MAC.

That means that first you calculate the MAC (mean aerodynamic cord), then measure back 10-15% of that from the LE.

There are several good MAC calculators out there on the web, if you google, I'm sure you can easily find one. You'll need to measure the root chord, tip chord, and wing sweep.

What you're finding is the average chord length and the spot on the wing that has that average. On most wings it works out to about half way out. On a pure delta wing, it's often 1/3rd of the wing. But you're best using one of the calculators out there.

If you feel lucky, you can eyeball it. You want roughly 10-15% of the wing area in front of the CG, so it's going to be pretty far forward. However, flying wings often have very critical CG's, and small adjustments often make for big changes in performance, so while I often eyeball conventional planes, I probably wouldn't try that approach with a flying wing.