In order to acquire access token perform following sequence:
~~~
use yii\authclient\OAuth1;
$oauthClient = new OAuth1();
$requestToken = $oauthClient->fetchRequestToken(); // Get request token
$url = $oauthClient->buildAuthUrl($requestToken); // Get authorization URL
return Yii::$app->getResponse()->redirect($url); // Redirect to authorization URL
After user returns at our site:
$accessToken = $oauthClient->fetchAccessToken($requestToken); // Upgrade to access token
~~~