Magento – OAUTH Flow in Magento2

The documentation on Magento's site has a good example here

Here's one of the examples that they give for creating a simple product as an Admin user with OAuth authentication.

session_start();
if (!isset($_GET['oauth_token']) && isset($_SESSION['state']) && $_SESSION['state'] == 1) {
$_SESSION['state'] = 0;
}
try {
$authType = ($_SESSION['state'] == 2) ? OAUTH_AUTH_TYPE_AUTHORIZATION : OAUTH_AUTH_TYPE_URI;
$oauthClient = new OAuth($consumerKey, $consumerSecret, OAUTH_SIG_METHOD_HMACSHA1, $authType);
$oauthClient->enableDebug();

if (!isset($_GET['oauth_token']) && !$_SESSION['state']) {
    $requestToken = $oauthClient->getRequestToken($temporaryCredentialsRequestUrl);
    $_SESSION['secret'] = $requestToken['oauth_token_secret'];
    $_SESSION['state'] = 1;
    header('Location: ' . $adminAuthorizationUrl . '?oauth_token=' . $requestToken['oauth_token']);
    exit;
} else if ($_SESSION['state'] == 1) {
    $oauthClient->setToken($_GET['oauth_token'], $_SESSION['secret']);
    $accessToken = $oauthClient->getAccessToken($accessTokenRequestUrl);
    $_SESSION['state'] = 2;
    $_SESSION['token'] = $accessToken['oauth_token'];
    $_SESSION['secret'] = $accessToken['oauth_token_secret'];
    header('Location: ' . $callbackUrl);
    exit;
} else {
    $oauthClient->setToken($_SESSION['token'], $_SESSION['secret']);
    $resourceUrl = "$apiUrl/products";
    $productData = json_encode(array(
        'type_id'           => 'simple',
        'attribute_set_id'  => 4,
        'sku'               => 'simple' . uniqid(),
        'weight'            => 1,
        'status'            => 1,
        'visibility'        => 4,
        'name'              => 'Simple Product',
        'description'       => 'Simple Description',
        'short_description' => 'Simple Short Description',
        'price'             => 99.95,
        'tax_class_id'      => 0,
    ));
    $headers = array('Content-Type' => 'application/json');
    $oauthClient->fetch($resourceUrl, $productData, OAUTH_HTTP_METHOD_POST, $headers);
    print_r($oauthClient->getLastResponseInfo());
}
} catch (OAuthException $e) {
print_r($e);
}

You can get OAuth Token by using below details:

URL : https://magento.local/rest/V1/integration/customer/token

Header : Content-Type : application/json

Request Type : POST

  **Params**--->
    {
            "email":"test@test.com",
            "password":"test@123"
    }

You will get customer token.