Google Apps Script: API authentication to Luno API

Hi guys! Total noob programmer here (originally an old-school mechanical engineer).

After going through all of Javascript lessons on Ivan-on-Tech, I thought I could try buidling a simple script on Google Sheet.
My project plan was to have a script to automatically track all of my transactions on Luno.com (cryptoexchange) through their API.
Their API documentation is here.

I was attempting to use List Transactions to populate all historical transactions on my spreadsheet, but I got stuck at the authenticate UrlFetchApp.fetch(url) endpoint access request
(e.g. myAPIkey = h8asdfasdgbn8w, myAPIsecret = F1Dn8sR19ybKfGIkfu3MasdfYSok4TUzVexm4A9QPJzk)
Below is my Code.gs script:

function importStatementLuno() {
  var ss = SpreadsheetApp.getActiveSpreadsheet(); //get active spreadsheet (bound to this script)
  var url = 'https://api.luno.com/api/1/accounts/h8asdfasdgbn8w/transactions'; //api endpoint as a string

  var response = UrlFetchApp.fetch(url,{'muteHttpExceptions': false}); // get api endpoint
  var json = response.getContentText(); // get the response content as text
  var lunodata = JSON.parse(json); //parse text into json

Logger.log(lunodata);

My fetch response gave me this Error:

Exception: Request failed for https://api.luno.com returned code 401. Truncated server response: Unauthorized
(use muteHttpExceptions option to examine full response)

I can’t for my life understand their documentation! I’m not sure if there’s actually different expressions used to provide authentication keys to their server (they explicitly mentioned they support Go better in their Get Started documentation)
I hope someone here could help me point out where I went wrong.