In the Web Portal, you can go to the Settings cog > Client Portal. If it is not activated on your account, you will see a popup message with a learn more link, as well as a button to Get Started. Select Get Started and a drawer will pop out on the right side of the screen with more information, the price of the module, and the Upgrade Now button
Select Upgrade Now to opt in. You can cancel the extra module any time by contacting accounts@formitize.com.