An insta is a bookmark made approximately 15km past the actual location to which you want to warp in the direction away from where you will be warping from. This allows you to warp the the actual location you wish to be at, instead of 15km away.
For instance, if you wish to create an insta at a space station to which you warp after mining an asteroid field:
- Warp from the steroid field to the space station.
- After arriving at the space, continue flying without changing your heading past the space station.
- Create a bookmark after the distance from your ship to the space station has increased to approximately 15km.
You can then warp directly to the space station from the mine field.