Checking the docs for that plugin, you can see:
Can admin add custom fields to the frontend submission form for the WP User?
No, Custom fields are not supported with this user-generated content plugin.
If you want something similar, you can either:
1) Do a custom form using the ACF plugin which can submit posts OR
2) Look at something like Gravity Forms. You can then submit posts but also link into custom fields (it even has an add-on to map the fields)
Welcome to the Advanced Custom Fields community forum.
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