We generally set it to broadside direction. If your CP is in tilted direction, then find the direction from the simulated data and plot the axial ratio (AR) at that direction. Measuring AR in one direction is not a good sign of research. For true CP, AR will satisfy the criteria at phi = 0, 45, 90 and 135 deg planes. Otherwise, it can be DP, we cant say anything.
Sounik Kiran theta = 0 deg (general case). For tilted beam, it can take different value depending on maximum direction of the beam. As I do not know your antenna, you can take theta = 0 deg (default value) for phi = 0, 45, 90, 135 deg planes