Firstly add the Buy button to your Sales Channels if you haven't already done so. You will find all the necessary information in the article on Adding the Buy Button sales channel. Now you can easily create a Shopify checkout link. Open the product's edit page to which you want to create a link. Now click More actions and select Create checkout link from the dropped-down menu.
Copy the created link to the clipboard. Have a look at the article on the checkout link if you want to link several products or different variants.
The next step is switching out to the Personal Discount app. You can add new automation or edit the existing one. Scroll down to the Redirect section. At this point, we need to modify our Shopify checkout link a bit. Personal Discount redirect creates a link that looks like this:
As we can see, there is one question mark in our link. The construction of the URL doesn't allow to use of further ones. So if there is another question mark in your checkout link, you need to remove it along with the part following it. Please look below:
And this is how you should fill out the Redirect section in the Personal Discount automation settings:
Select the option that you want to redirect to another page within your store and paste the proper part of the URL.
As a result, customers will be redirected to the checkout with the discount code applied.