settings error

[Giladx]

Since Pagekit-cart was not on the marketplace I installed it manually by uploading the source to packages/bixie.
I enabled it
when I go to settings I get this error
Fatal error: Class 'Omnipay\Omnipay' not found in /home/gilad/public_html/packages/bixie/pagekit-cart/src/Payment/PaymentHelper.php on line 100

 1/1- `ClassNotFoundException in PaymentHelper.php line 100: Attempted to load class "Omnipay" from namespace "Omnipay".
Did you forget a "use" statement for another namespace?`

Thanks