Once you have created variables for each parameter they must be added to the end of the URL. Manually add parameters and variables or use the Google URL Builder here: https://ga-dev-tools.appspot.com/campaign-url-builder/
Example:
Take the website https://pontiac.media and add the above variables: https://pontiac.media?utm_source=PONTIAC&utm_medium=display&utm_campaign=Remarketing&utm_content=Creative1-300×600
When you upload creatives to the Pontiac platform, use the new URL with UTM parameters & variables as the click URL. You can then view reporting broken out by these variables in Google Analytics. 
In the Google Analytics dashboard, use the ‘Acquisitions’ -> ‘All Traffic’ -> ‘Source/Medium’ report to see where traffic on your site is coming from. Traffic driven by a campaign with the above click URL would appear in this report as  ‘Pontiac / display’.