How to add payment gateways

I have version 1.5.5, the problem is that I only have the following payment methods:
online payment

How can I add the PayPal Express option?

It is a fantastic program and I am using it.

Thanks!!

Regards, Josep.

PayPal Express is already available… you may scroll down that provider list?

Sorry, I had not seen the scroll. I had gone crazy looking how to do it.
Thank you!!

Greetings,
Josep.