There are a few ways to get to GrimHex. If you have a wanted rating you can simply spawn at GrimHex once you die. Alternatively, if you have a wanted rating you will also see GrimHex in your quantum travel options as a destination.
If you do not want a wanted level and would like to travel to GrimHex the easiest way to get there from Port Olisar is to quantum travel to the ICC probe and then quantum travel to Yela. When you arrive at Yela you will be facing the moon, simply turn to the ring of asteroids to the right and from there head straight towards a dense pack of asteroids and keep navigating through the asteroids straight ahead to reach GrimHex.
Step 1 Quantum travel from Port Olisar to the ICC Probe
Step 2 From the ICC Probe quantum travel to Yela asteroid field.
Step 3 At Yela asteroid field fly towards a dense collection of asteroids which is to the right of Yela Moon (see images below).
Looking to get from Port Olisar to GrimHex? Find out how without a Crimestat rating.
For details on how to get to GrimHex please watch this video from BoredGamer (More great vids from BoredGamer available here: https://youtube.com/user/BoredGamerUK):
Finding Grimhex Made Easy (by STLYoungblood)
Another method to get to GrimHex in under 1 minute from Port Olisar (Video from Admiral Khaaan)