With ClickBank there are two options for how your customers can checkout:
Direct ClickBank Checkout (recommended)
With the Direct ClickBank Checkout method, you can use ClickBank purchase links. When customers click on these links they'll be taken directly to the ClickBank checkout page to complete their order. This is the recommended method to use as it creates the quickest checkout experience for the customer. Read this article to learn how to create ClickBank purchase links.
Standard MemberMouse Checkout
With the Standard MemberMouse Checkout method, you'll use standard purchase links. When customers click on these links they'll be taken to the MemberMouse checkout page where they'll fill out the form, click the 
button and be taken to the ClickBank checkout page to complete their order. While the Direct ClickBank Checkout method is recommended, there are certain scenarios where you'll want to use the Standard MemberMouse Checkout method. One benefit of using the Standard MemberMouse Checkout method is that when the customer is sent off to ClickBank, a pending account is created in MemberMouse which allows you to collect additional data as part of their registration using custom fields.
IMPORTANT: When using this method the email address that the customer enters in the ClickBank checkout form must match the email address they entered into the MemberMouse checkout form exactly. If the email addresses don't match, two accounts will end up being created, one for each email address. If you're going to use this method, it is recommended that you add messaging to the MemberMouse checkout page informing the customer that the email address they enter needs to be the same one that they'll enter when they checkout on ClickBank.