HTTP POST method help for Node MCU esp8266

Hi all,

Please help me with the Integration of Node Mcu for POST request

I have a userId and Password grant type method for OAuth 2.0,

and with URL parameters

like: https://login.salesforce.com/services/oauth2/token?grant_type=password&client_id=-----------&client_secret=--------&username=rak@---.com&password=------

I getting Response from "Postman" but am new to Arduino coding

I have used this process for POST method but it is not working fine

HTTPClient http;
String str="url for POST req like above mentioned";
Serial.print("str "+str);
http.begin(str);
int httpCode = http.POST("");
if(httpCode > 0) {
if(httpCode == HTTP_CODE_OK) {
String payload = http.getString();
Serial.print("payload "+payload);
}
} else {
}
http.end();

Thanks in Advance !!!