How to get the base url for the Zap polling url?

I wanted to know if I can create an Infusionsoft app in Zapier.
I wanted to add another ACTION for an Infusionsoft app.

This is very specifically a Zapier question and not an Infusionsoft question. Have you contacted them? There process is to setup a connection to your app and then setup your filters and actions in regard to that app… they would be the ones that can help you best with their product.