Rest API Using Authorization Key

Question

This is first time i have started working on Rest API's

 I have tried a lot to find resources but couldnt achieve

 

as per documentation This has to be my request header and request will be POST

 

" Authorization":"125THIS123IS123TEST1354",

"cache-control":"no-cache",

"content-type":"application/json" 

 

I have tried alot to send data but got 401 Unauthorized error.

 

$.ajax({
           type: "POST",
           url: 'https://testurl/api/test',
           headers: {
               'Authorization': '125THIS123IS123TEST1354',
               'content-type': 'application/json',
               'cache-control': 'no-cache'
           },
           success: function (data) {
               alert('success')
           },
           failure: function (msg) {
               alert(msg);
           }
       });

I dont know am going on right way or is ther eany other method.....