Every instance of WWW with a second parameter is a post.
Here is an example to post user id and password to server.
void Login(string id, string pwd)
{
WWWForm dataParameters = new WWWForm(); // Create a new form.
dataParameters.AddField("username", id);
dataParameters.AddField("password", pwd); // Add fields.
WWW www = new WWW(url+"/account/login",dataParameters);
StartCoroutine("PostdataEnumerator", www);
}
IEnumerator PostdataEnumerator(WWW www)
{
yield return www;
if (!string.IsNullOrEmpty(www.error))
{
Debug.Log(www.error);
}
else
{
Debug.Log("Data Submitted");
}
}