To trigger a start event in a process app, please do the following:

1. Change the type of the start event to a message start event. Configure it like this:

You can change the message name to something that suits your need and also use multiple start events.

2. Invoke the start event via the API by: POST{process application id}?message=START.

Send parameters

You can also send parameters together with the POST that will be passed into the process instance. Do that in the following way:

1. Create a form in the process app that should contain your data.

2. Add fields to the form and make sure that you set correct names on each form field that should contain data.

3. Associate the form like on the picture below.

4. Start a new instance by doing the same call as above, but set the content-type of the HTTP call to application/x-www-form-urlencoded and add all parameters to the request body on the following format (URL-encoded): parameter1=value1, parameter2=value2 etc...

5. Any parameter that matches a field in the form associated to the start event will automatically be stored in the form, which will be accessible in the process instance, both via the API and via the user interface.