The Define/Modify Global Rotation Axis button is found on the Turbo workspace's Initialization view. When you click that button, the Define/Modify Global Rotation Axis dialog box appears.

Exactly one axis of rotation method must be specified. The axis definition can come from the results file, or it can be specified manually as either a Rotation Axis (six Cartesian coordinates) or a Principal Axis (X, Y, or Z). Upon changing the axis definition, the axial, radial, and Theta coordinates (and their dependent objects and expressions) are automatically updated. For details, see Theta.