Multiple states can be created for buttons and other elements. Learn more about ways to use component states here.
The final interaction will be to link over to the shopping cart or product page. Since this guide is covering the creation of the product landing page, and the Check out page, a link can be added from the Add to Cart button and treated like a Buy Now button, but you can expand on this and add additional pages using the elements in the UI Kit.
Start by creating a blank artboard for the checkout page (this will be developed next). In this case, all of the Add to Cart buttons will go to the same place, so we can apply the interaction to the Main Component. However, if these were to go to unique pages as part of a flow, set the prototype links to the individual instances instead.
Select the button in the Main Component hover state (it will be clicked while hovering). In Prototype mode, drag the blue arrow until it snaps to the newly created Checkout Page. That is all there is to it - you have now created a page link. The transition type, easing and duration can all be edited in the property inspector on the right. To keep it simple use a dissolve or slide transition. Learn more about prototyping in this getting started video.