Paypal payment - How to apply access token using paypal PHP SDK

I am trying to implement PayPal payment using the access token. For this, I obtained the token and refresh token from our customer's PayPal account, when they are connected. I have successfully created the token using the refresh token and trying to create the payment with that token. I am not sure how to set the token in the Paypal PHP SDK.

$access_token = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX';
// obtained using refresh token

$payer = new Payer();
   $payer->setPaymentMethod("paypal");

$amount = new Amount();
$amount->setCurrency("GBP")
   ->setTotal(1);
$transaction = new Transaction();
   $transaction->setAmount($amount);

   $baseUrl = base_url();
$redirectUrls = new RedirectUrls();
$redirectUrls->setReturnUrl("$baseUrl/customer/paypal/complete?success=true")
   ->setCancelUrl("$baseUrl/paypal/complete?success=false");
   $payment = new Payment();
$payment->setIntent("sale")
   ->setPayer($payer)
   ->setRedirectUrls($redirectUrls)
   ->setTransactions(array($transaction));

  $request = clone $payment;
    try {
       $payment->create($apiContext);
     } catch (Exception $ex) {    

   }

Here I have the access token, But I don't get any method to apply this access token in this code. Does anyone know how to make payment using the access token?