The first thing you need to do when designing your own automation workflows is determine the type of Trigger that will set your automation in motion. There are various types of triggers available - what the "When someone clicks on a specific link in a specific campaign" type does is get your automation fired up when someone clicks on a specific link inside a specific campaign.
There are two parameters that you need to define on this type of trigger:
1. You need to choose whether the automation will be triggered for every click your subscriber makes, or whether it will be triggered on the first click only.
2. The second parameter you need to define is the link that your subscribers need to click on to trigger your automation.
You can choose one of the available links from the drop-down menu. Keep in mind that only clicks on this specific link will trigger the workflow. After you're done, click on the Save button to have your trigger ready and waiting inside your workflow.
This was the first step to create an automation which will be triggered when someones clicks on a specific link in a specific campaign! Take a look at how the available Conditional / Control steps will help you move forward with your design and how to work with the various Actions.