Post Request advanced editor

Hello I want to connect to data on my webservice

I need parameters in the body clause: user, password, clientId

I wrote this c# code in postman:

var client = new RestClient("h**p://******.c*m/provision/user....htm*");
var request = new RestRequest(Method.POST);
request.AddHeader("Postman-Token", "c153f34d-5c8b-46dd-b9e7-7901aa6e62fc");
request.AddHeader("cache-control", "no-cache");
request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
request.AddHeader("content-type", "multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW");
request.AddParameter("multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW", "------WebKitFormBoundary7MA4YWxkTrZu0gW\r\nContent-Disposition: form-data; name=\"user\"\r\n\r\nUSER\r\n------WebKitFormBoundary7MA4YWxkTrZu0gW\r\nContent-Disposition: form-data; name=\"password\"\r\n\r\nPASSWORD\r\n------WebKitFormBoundary7MA4YWxkTrZu0gW\r\nContent-Disposition: form-data; name=\"clientId\"\r\n\r\nCLIENTID\r\n------WebKitFormBoundary7MA4YWxkTrZu0gW--", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);

But i didnt know how to use it in the power query editor. Some code example to transform my code?

Thanks a lot