3.click on "Test Account"
4.click on Preconfigured account after this choose account type(select buyer) and insert details
5.now you have to do same once more time but now you will select the seller account type and fill all the required details.
6.note down the username and passwords of buyer accounts on "test account page".
7.now click on API CreDentials and note down the detals like this examples:-
API Username: username_biz_api1.gmail.com API Password: password Signature:ursignature
Click here to Register and to get complete example.