Change the button onclick function of button on home page

[Ahsan-]

Hello,

I'm using the Broadcast theme for this store. I have added a section to the home page named 'image with text'. There is a button in this section as can be seen in the attached image. The theme only allows to attach links to the product page or some other page. 
I want this button to function as a 'Buy It Now' button. Specifically, I want it to add the product to the cart and then redirect customers to the checkout page. Since there's only one product in the store, this should be straightforward. Can you help me achieve this?

[Ahsan-]

https://digplanner.com/

[Ahsan-]

Yes, I'm familiar with Shopify design. Please go ahead.