VoLTE doesn't need you add any features via your Verizon account. It will just use VoLTE when it can. Verizon VoLTE requires you to be in a VoLTE area, on a capable VoLTE device, and be calling someone else on Verizon who also is on a VoLTE device in a VoLTE area. Otherwise it will just use the old standard for the call.
The instructions for activating it on other phones have you going into VZ and selecting the advanced calling feature for $0.00. That feature is not an option on the Note 4.
From VZ FAQs:
"If you’re eligible, follow these steps to get Advanced Calling 1.0:
Go to the Change Features page in My Verizon.
Note: If you have multiple lines on your account, select the line you want to add Advanced Calling 1.0 to.
Click Add next to the HD Voice feature and click Next at the bottom of the page.
Follow the onscreen prompts to finish adding HD Voice to your account.
Note: If you have any features that are incompatible with Advanced Calling 1.0 on your line, you’ll be shown a list of them before you complete your transaction in My Verizon. These features will be removed from your line when you add HD Voice. If it includes a subscription service that gets charged monthly, you’ll be refunded the prorated rate of the service for the remainder of your bill cycle.
Once you’ve added HD Voice to your line, restart your phone to begin using Advanced Calling 1.0.
You’ve successfully added Advanced Calling 1.0."