Hello, MarinaSobolieva. Thank you for using the Apple Support Communities.
We understand your question and how you are looking to use the Side Button on your device to access your Apple Pay cards. We’re happy to help you with this!
To start, we’ll want to be sure that the correct features are enabled in the Settings app of your iPhone.
If you are using the most recent version of iOS already, please open Settings > Wallet & Apple Pay. Scroll down to be sure that “Double-Click Side Button” is enabled here.
If you are already seeing this option enabled, please disable the option and restart your device. Once your device has started again, enable “Double-Click Side Button” in the Settings app once again.
We hope this answer helps you find a solution. Please let us know if you have any other questions.
Enjoy!