you can use android mobile app or use laptop ,if you use laptop , you will need usb dongle to connect with j10 hearing aid via ble,if u use mobile app, u can download from google playstore or appstore, or direct download link : https://www.jhearing.com/web2/docs/fota%20demoapp-release.zip

upgrade via onsemi ble explorer , in step u , u click update firmware , it will prompt u to select the .fota file

this is sample screen shot , you need plugin usb dongle ,in my laptop ,it appearas as COM3,and the .fota file is the upgrade firmware file

I attached a sample fota files ,and hex files at https://www.jhearing.com/web2/docs/J10_1028_how_to_fota.zip