If you have a CSV file which looks like:

Textual representation:
action,contract,company,job_number,timestamp
CN,138484833,B,1234564,2020121710470000
DN,138484834,C,1234565,2020121710480000
EN,138484835,D,1234566,2020121710490000
You can build your request using the data from the file as follows:
Add CSV Data Set Config as a child of the request you want to parameterize
Configure it as follows:

In the "Body data" tab of the HTTP Request sampler use the following syntax:
{
"action": "${action}",
"contract": "${contract}",
"company": "${company}",
"job_number": ${job_number},
"timestamp": ${timestamp}
}

That's it, each virtual user will read the next row from the CSV file on each iteration and substitute JMeter Variables placeholders with the real values from the CSV file
