How to assign ISM policy to existing indices

Hi Team,

I have indices by name proapps-* and have created a below policy to it. Can someone please guide how to attach the policy to existing indices already created?

{
    "policy_id": "ProApps-Policy",
    "description": "hot warm delete workflow",
    "last_updated_time": 1633492037659,
    "schema_version": 1,
    "error_notification": null,
    "default_state": "hot",
    "states": [
        {
            "name": "hot",
            "actions": [
                {
                    "rollover": {
                        "min_index_age": "1d"
                    }
                }
            ],
            "transitions": [
                {
                    "state_name": "warm"
                }
            ]
        },
        {
            "name": "warm",
            "actions": [
                {
                    "replica_count": {
                        "number_of_replicas": 2
                    }
                }
            ],
            "transitions": [
                {
                    "state_name": "delete",
                    "conditions": {
                        "min_index_age": "90d"
                    }
                }
            ]
        },
        {
            "name": "delete",
            "actions": [
                {
                    "notification": {
                        "destination": {
                            "chime": {
                                "url": "<URL>"
                            }
                        },
                        "message_template": {
                            "source": "The index {{ctx.index}} is being deleted",
                            "lang": "mustache"
                        }
                    }
                },
                {
                    "delete": {}
                }
            ],
            "transitions": []
        }
    ],
    "ism_template": null
}