Turning on call waiting on Nexus 6p.

[ttthom]

Looked under settings and there isn't a place to select.

 

[Haythom]

Press Phone Icon then from top on right select menu ===>> Settings ===>> Calls ===>> Additional Settings ===>> Check Call waiting .... That's It

 

[redduc900]

If you're using Project Fi, call waiting is enabled by default. Also w/ Project Fi, there is no 'Additional Settings' option under Settings--> Calls. Only Calling Accounts, Voicemail, and Wi-Fi Calling options. And under Phone Settings--> Sounds and vibration, make sure you also have 'Also vibrate for calls' selected.