PowerBI embedded token individual key

Hi guys,

I'm new to PowerBI and I have a question regarding Post request method,

we have a service API that we like to use PowerBI to connect to get data where clients and do reporting,

we tried to setup a connection between powerbi desktop and our API through Post request

let

body = "{""username"": ""xxxxxxxxx"",""password"": ""xxxxxxx"",""grant_type"": ""password"",""something"": ""test"",""clientsomething"": ""passwordhere"",}",

url = "https://xxxxxxxxxxxx/token",

GetJson = Web.Contents(url,      [

         Headers = [#"Content-Type"="application/x-www-form-urlencoded"],

         Content = Text.ToBinary(body)

     ])

in

GetJson

We can get into the api and see some value but what we have problem is  where do I put in the values for individual key and how do I also send in a request body that's recognized by PowerBI? 

Thanks