How to find Steinmetz parameters from datasheet?
The core loss equation is in the form \$P_{loss}=a\times B_{pk}^b \times f^c\$.  

Where \$P_{loss}\$ is the core loss density, \$B_{pk}\$ is half the AC flux swing, and \$f\$ is the frequency.  \$a\$, \$b\$, and \$c\$ are constants for the given material.

The data sheet for the material gives you curves for \$P_{loss}\$ vs. \$B_{pk}\$ and \$P_{loss}\$ vs. frequency at different values of \$B_{pk}\$.  

From there you can use a curve fitting routine (Matlab, Mathcad, hand calculation, etc.) to get the constants.

It may be easier to call or email applications support for the product and see if they can help you.