How to enable Car mode in Samsung Galaxy S5(SM-G900H)?

a). Pull down the Notification Panel using two fingers as shown below :

b). Tap on Car mode and then tap on Start as shown below :

c). Read the terms of Service and tap on I agree as shown below :

d). Tap on Next after accepting terms of service and then tap on Next as shown below : 

e). Tap on Yes to accept the Bluetooth permission request as shown below :

f). Tap on Next after reading the guide and then tap Start as shown below :

Car mode is enabled in Samsung Galaxy S5.

You have to follow the set up steps when accessing the Car mode for the first time.