How to add ccavenue donate button in wordpress?

I am new to payment gateways integration, I want one donate button which will be processed by ccavenue, user will need to type the donation amount, I want the overview of How I’ll integrate it? what plugin, API, Extension, Theme, Custom code change I’ll need to do.

I tried to contact ccavenue team but they are not available, Their servers are down. I tried to watch youtube videos, but all videos are about paypal donation button integration, But my client is demanding only for ccavenue donate button.