Qfyilyi

As explained in @karthikeyan's answer the InSight lander will rely upon its landing system to orient the lander properly, so that once on the ground instruments such as the RISE antennas will be pointing in the proper direction, in this case roughly East and West, more specifically, towards Earth when InSight is near the edge of the planet's disk as seen from Earth.

From this short conference paper:

For RISE, Doppler measurements will be made at times when the Earth is at low elevation, when the Doppler signature due to the rotation of Mars is largest. Two fixed medium-gain antennas, one pointed to the east and one pointed to the west, will be used to provide adequate gain for RISE.

While InSight is still moving horizontally with high velocity during its entry, it has its velocity vector (from whence it comes) as a reference with respect to the terrain. But very near the end of its seven minutes of terror, in the final hover and drop, what reference will it use for lateral orientation (rotation about the vertical)?

There's no useful planetary magnetic field for direction-finding. Is it known what cues the landing system will actually use to orient InSight correctly?

By integrating inertial measurements, initialized from the final star tracking about 20 or 30 minutes earlier.