Unable to push documents and index patterns in indexes in kibana plugin using core api

Elastic Stack Kibana
1

I am unable to push the documents in the newly created index and add new fields to it using the kibana core API . Although I was able to do it with the dev tool. i want to implement this feature in my plugin to add documents and add new fields to it.
Something like this -
POST index name/type
{
"document1":"value"
}

Screenshot 2021-06-24 at 3.53.59 PM
Screenshot 2021-06-24 at 3.53.59 PM1238×262 44.3 KB

2

any suggestions on this one?