How can I get the access token?

Hi, i want to get an access token. but i can't.

I post four parameters to Bing translate API address by useing advanced Rest client which i can download at chrom web store.

these are  API address and parameters which i put in the advanced Rest client.

api address: https://datamarket.accesscontrol.windows.net/v2/OAuth2-13

parameter

client_id : saTranslator

client_secret : 3t****G+qj1LL1IeSQ4****************

scope : http://api.microsofttranslator.com

grant_type : client_credentials

but i can't get the result.

am i wrong?