Answer:To turn on the 7th DOF, while defining the section check on the
Consider warping effect option as shown below:

Once the 7th DOF is turned on in the section properties, then the program will calculate the below properties in addition to the usual properties.

This can be verified by clicking on
show calculation results option as shown below:
Then the program will calculate the Bi Moment (W), Twisting moment (Mt), and Warping moment (Mw).

After that program will calculate the stresses accordingly as shown below.

For more details on this, kindly refer to the attached pdf document