To set up marketing options for your stores
Simply go to Stores > Store Settings > General
Scroll down the page to find Marketing Opt-In. Switch on “Show a marketing signup option at checkout”.
Opt-in text can be customised. Keep it short and simple. This message will appear at checkout. Don't forget to press Save to apply the changes.
You can also find a list of customers that gave you permission to use their data under Customers. Click on Export.
In a few minutes, you will receive an email from email@example.com with the subject “Exported customers”. Open the document and look for the column with the title Policy Agreed. If it states TRUE, it means the customer gave you permission to use their data for marketing purposes.
To check your marketing reports go to Reports > Marketing
Here, you have a chart of visitors by date. Check where your visitors come from under the Marketing Sources tab and how many of those visits converted into sales under the Sales by Source tab.
If you have multiple stores, select the store you're checking reports for in here. (Select store button) on the top right corner.