LinkedIn does not have dynamic parameters available so you need to manually set the parameters manually for the comet_campaign and comet_ad_id parameters on the Destination URL.
comet_source=linkedin (should always be set to linkedin)
comet_campaign=XXXXX (should always be the LinkedIn Campaign ID)
comet_ad_id=XXXXX (should always be the LinkedIn Creative ID)
Finding the Campaign ID and Creative ID in LinkedIn Ads Manager
After your campaign has been published, you have to go back in and edit the Destination URL:
Finding the Creative ID
Each ad has it's own Creative ID. You can find the Creative ID by clicking into your ads. You will notice in the screenshot below that each ad has it's own ID, you must use each ID next to the red arrow for your comet_ad_id parameter.
Finding the Campaign ID
Each campaign has it's own Campaign ID. You can find the Campaign ID by clicking into your campaigns. You will notice in the screenshot below that each campaign has it's own ID, you must use the ID next to the red arrow for your comet_campaign parameter.