To enable "Kwik Buy settings", go to:

Campaign>Quick Buy settings

In a regular case, once the buyer clicks on Buy now, it leads him to:

Cart>Checkout page> Payment Gateway> Thank you page

If you want to lead your customers to making the purchase quicker, you can enable Kwik buy settings. 

Step 1: Enable Kwik Buy by selecting the radio button 

Step 2: Where to redirect buyers:  You have the option to redirect buyers to either cart page, checkout page or even define a custom URL which could be any link including external and affiliate links.

Step 3: Button Text: You need to define the text you want the customers to see in the Kwik buy page. "Buy now" could be one option    

Step 4: Clicking on Save settings and it will save all your settings.