The YouTube subscription button is a total win.
This button has two main functions: First, your client will be able to visit your YouTube channel from your Fastcard. Second, if they are already logged into their YouTube account, they will instantly become subscribers to your channel when clicking the button.
Add this action to your Fastcard with these steps:
- Go to your Fastcard and click on "Edit."
Click on the "Links" button.
A list of actions you can add will be displayed. Choose the "Subscription" action with the YouTube icon.
Write the title or a name for that action. It could be just "YouTube" or something that indicates that's for your Fastcard visitor to subscribe to your channel.
A subtitle is optional. It could be your channel's actual name if you didn't use it as the title.
Add the button text. No ideas? "Subscribe" might be ok.
Now copy the exact link of your YouTube channel and paste it.

Note: If your client isn't logged to their YouTube account, they will be asked to log in, and they will have to subscribe to your channel manually. If they are logged, they will instantly become subscribers when hitting the button on your Fastcard.
Don't forget to check that the link you are adding is exactly the same link that will take your clients directly to your own channel and not just any page on YouTube.

Tip: Do you see the arrows on the action? Those arrows will help you set and organize the action buttons that will be shown on your Fastcard. If you want your YouTube button to be on top, just move it upwards by clicking on the arrow.