If you want to purchase Tuya modules for development, you need to log in and register on Tuya Smart Platform: https://iot.tuya.com/to create the products you need to develop. You can purchase testing modules online in the third step 'hardware debugging' page. Click "Buy Module-Submit Order" to complete the payment online. If you meet other problems during development, you can submit problems on the page. Tuya has a professional technical support team to respond to your problems efficiently.