Public payment app extension approved but not visible in checkout page to select as option for pay

[manaw]

Hi, 

I have create a new public app and created  app extension and published it as it was approved.

However I am not able to activate this extension and it is not available for checkout on my development store as well.

 Can someone please help me with the process? I have few queries, If extension is approved and visible, how can we activate it in Alternative payments provider area of shopify admin? Before submitting app for approval I would like to do test checkout with my off-site paymenr provider app extension.

Please help me with process or queries, it would be really great for me to proceed further with my public app.