Turn it on in Company Profile → Photos & Video Notice (Settings → Company Profile & Proposals on the office web page). It's off until you turn it on.
What the customer sees
A Photos & Video section on the proposal (the PDF and the accept page):
On the accept page there's a box: Opt out: Please don't use photos or video from my property for marketing or training. Customers who sign a printed proposal can check the box printed under the notice.
You can write your own wording. Use [company] where your name goes. Have a lawyer look it over.
Where the answer goes
The customer screen: under Photos & Video (app) or on the customer's page (web), with who answered and when.
The crew job sheet: a red line at the top, No marketing photos or video. Photos for the job record (before and after, damage) are still fine.
The accepted email you get says when a customer opted out.
The next proposal for that customer starts with the box already checked. If they uncheck it when they accept, that's their new answer.
Recording it yourself
If a customer tells you in person or on the phone, turn on Opted out of marketing photos on their customer screen. It's saved with your name.