Authenticate before posting

I need to authenticate with the API and receive a token before I can post data. Not sure how I can do this with this plugin. The process is:

Step 1: POST login credentials
– body is json containing username and password (hard coded)

Step 2: Receive response
– response includes token

Step 3: POST form data
– header includes token received in step 2
– body is json formatted form data

I’m looking for documentation on how to get the response and integrate it into a second POST. Thanks.