1. Place addons file into /whmcs/modules/addons/
2. Place gateways folder files into /whmcs/modules/gateways


Activate Addon from Admin Area -> Setup -> Addon Modules and Configure with details 
Activate Gateway from  Admin Area -> Set up -> Payment gateway 



Additional things are : Now you have ability to do more automation 

1. Invoice Marking Paid : Invoice Marking Paid
2.Order Marking as Accept:Tick if you want Order to be marked as Accept once details get validated
