1. Double click on Json on the right side of the pane.
2. Select the Json file.
3. Select the schema levels. ( Depth till which you want to use in data source for data visualization. )
4. Click on sheet to use the Json data. You can re-select the schema levels you want to use by edit connection.
5. Now you can use Json data.
For more information, https://onlinehelp.tableau.com/current/pro/desktop/en-us/examples_json.htm