In Game Use

Once you get in the Vehicle the Grappler GUI should appear on your Display.

To Deploy the Grappler you can either use the Deploy Button or press the Quick Deploy key which by default is "J".

Once Deployed and Armed you can choose to Stow it again by pressing the Disarm and Stow Button.

If you managed to Grapple a vehicle you can use the options on the right to increase/decrease the distance between you and the vehicle. Or Release it completely.

After this you will need to Reset your Ropes by going the front of the vehicle and interacting with the Prompt at which point you can Stow it again for futher use.