Product attribute create/update using rest api and assign it to attribute set

I am creating product attributes using rest API with the below request body. End point rest/V1/products/attributes/

    {
  "attribute": {
    "is_wysiwyg_enabled": false,
    "is_html_allowed_on_front": false,
    "used_for_sort_by": false,
    "is_filterable": true,
    "is_filterable_in_search": true,
    "is_used_in_grid": true,
    "is_visible_in_grid": false,
    "is_filterable_in_grid": true,
    "position": 0,
    "apply_to": [],
    "is_searchable": "1",
    "is_visible_in_advanced_search": "1",
    "is_comparable": "1",
    "is_used_for_promo_rules": "0",
    "is_visible_on_front": "0",
    "used_in_product_listing": "1",
    "is_visible": true,
    "scope": "global",
    "attribute_code": "text_api_attribute",
    "frontend_input": "text",
    "entity_type_id": "4",
    "is_required": false,
    "is_user_defined": true,
    "default_frontend_label": "Att Label updated",
    "frontend_labels": null,
    "backend_type": "int",
    "default_value": "",
    "is_unique": "0"
  }
}

it's get created successfully but how can I assign this attribute to the attribute set.tried with group: General but its not defined in interface so it throw error.

also there is an error when try to update using PUTmethod rest/V1/products/attributes/rest/V1/products/attributes/

{
"message": "%1 already exists.",
"parameters": [
    "Attribute with the same code"
]

}