First click 'Websites', then 'View Websites' on the left hand side of the dash board.
Click 'Edit' next to your website.
Click on "Opt-In Prompts" on the left side of your dashboard.
Select "Page-Specific Logic (Advanced).
Then select "Add Condition".
Change the Auto Prompt field to "false" and then click add condition. Now the condition is active and your Opt-In prompt will not be displayed on the pages that you have chosen.