How do you do a Hard reset on iPhone 6s

What do you mean by a hard reset? That term is not part of the troubleshooting steps. There is restart, reset, restore from backup, restore to factory. A reset here is holding the sleep/wake and home buttons together until you see the Apple logo and then release. The phone will reboot. No data is impacted in this procedure.

Reset your iOS device to factory settings - Apple Support

anything past this is not recommended for a user to modify and you should bring the device to Apple otherwise you could void any warranty and any further possibility of having the device repaired by an apple authorized service center under any circumstance.

Help

Help with what? You are trying to reset your iPhone?