After you create a Slack connection, you can use it in a Service step in a process.
1Add a Service step to the process.
2Click the Service tab.
3From the Service Type list, select Connection.
4From the Connection list, browse and select the Slack connection that you created.
5From the Action list, select the action that you want to perform. For example, select the Upload File action to upload a file to an external URL returned by the files.getUploadURLExternal method as shown in the following image:
In this case, Application Integration populates the url and file objects under the input fields and the statusCode and response objects under the output fields.