How to show an Onsite Form to visitors from specific traffic sources

1. First, you need to create a form. If you haven't already, check this article. You can also select one existing form, by clicking on the Campaigns tab from the main menu and then clicking on the form that you want.

2. From the Editor view, click on the Visibility tab, as shown in the picture.

3. From the Visibility view, you can also set your form's trigger, frequency and targeting. 

4. From the Browsing rules, click on the Traffic Source box.

5. After clicking, click the toggle button to enable the rule and select your relation from a drop-down menu and source by typing the URL in the input box.

6. Don't forget to press enter after typing your source, for the rule to work properly. Your screen should look like the photo below.