How can I add another shop to my Tpay account?

To add a new shop to your account, please add the website to your Merchant Panel and integrate it the same way as you did it with your first shop. 

However, there is no possibility to turn the test mode on at only one website. To do that you would need a separate account for each shop. 

Also in case of using Click Shop/Shoper module, there is no possibility of adding more than one shops to one Tpay.com account.