URL parameters are added at the end of the URL you'll be putting as the destination for your ad. They can help you understand the effectiveness of your ads. 

For example, you can use URL parameters to identify where your ad traffic is coming from and which ads helped drive a conversion.
The information coming from URL parameters can show which link people clicked to get to your ad's destination, like to your website or Facebook Page for instance!

Keep in mind that although you can add URL parameters to your ads on Paragone, you'll need to use a website analytics tool to track the results.

To set them up, you'll simply need to prepare your link and put is as the Destination Link in the Campaign Creation Flow, in the Creatives step. 

Your link should look link this: https://makemereach.com?a=&1b=2

First you'll need to get down to the ad level (in your Dashboards or Campaign Reports). Once you've selected the ad(s) you want to modify the URL parameter of, get to the action bar and select "Edit the URL parameter": 

Once you click on that option, you'll get access to a small window with the current link, and you can modify as you want to!