How to add my debit cards to my Apple Wallet?

Have a look at the steps mentioned in this article:

Set up Apple Pay - Apple Support

And your banking institution has to support Apple Pay:

Countries and regions that support Apple Pay - Apple Support

Did you already click on the blue links above your post?

This will open an article, explaining all the steps needed.

I would like to add a debit card to my account

I would like to add a debit card to my account