Error while access the token

[sandeshchand87]

Hello Sir, I am getting error while getting token . i am following your tutorial for getting the tokens.
{
"developerMessage": "The client_id (application key)/client_secret are not valid",
"errorCode": "AUTH-003",
"more info": "https://forge.autodesk.com/en/docs/oauth/v2/developers_guide/error_handling/"
}

while creating the app in autodesk forge,what is the callback url?