If you want to easily add a button that opens a Stripe checkout on your page, you can use the third party service Commence Payments. You can find them at https://commencepayments.com/
How it works
The first step is going to their website and creating an account. After that is done, you will be asked to connect to your Stripe account. Then, Commence Payments will provide you with a sample code to create a payment button or you can use their generator to create a custom button to your specifications.
On the Instapage side, you just need to add the code they give you in an HTML widget:
Then you just need to Save and Update your page to push the changes live. Here's what it will look like on the page:
Note: While we try to keep all of our instructional articles that involve third-party services up to date, sometimes they make changes to their platform of which we are not aware and, as a consequence, the user interface may differ from the provided screenshots.