How to develop a buy now, pay later payment option?

[smassesgn72]

Hi, 

I'm building a buy now pay later option for a specific country, where shopify has not be used much. 

What is the best way to develop it and get it approved ? an App or an Alternative payment methods (which is down at the moment) ?

Is there a process to follow as some of my existing customer are already using shopify and want to use our BNPL option.

A guidance will be useful

Cheers