As the trigger action pick an HTTP Request action.
Then head over to http://jsonschema.net/#/ to generate the swagger JSON schema needed. Just enter your JSON object, any way you want, click generate schema, and copy paste the output into the Flow action.
Your object properties are now available to use in a new action, as the one picture below where we create a new CRM record.
Once you save your Flow, you can copy the endpoint URL and do a POST with your JSON object to that andpoint and you’re ready to roll