To enable double opt-in:

1. Click Settings icon on the top-right corner of the screen, then click Double opt-in under Consent and privacy.
   
   
2. Enable the double opt-in toggle. This will open up the consent email configuration.
   
3. Click Edit icon on the right and enter the following details:
   
1. Sender address - Select a sender address to send the email.
   
2. Subject - Enter a suitable subject line. Click Personalize if you wish to add merge tags to your subject line
   
4. Click Save.
   
5. Click Edit icon on the right to create email content.
   
6. Draft the email as per your requirement in the email editor
   
7. Click Save and close. 
   

To disable double opt-in, disable the toggle and click Proceed.