Pretty self-explanatory, but here's how to do it in 6 easy steps :
1. Load into any server of your choosing.
3. Pick any class with a grenade (Rifleman is a good choice.)
2. Spawn on any outpost or garrison of your choosing.
4. Press "G"
5. Here's the tricky part, pay attention - Look down at your feet, click RMB, wait for a second and release RMB.
6. Profit!