You need to contact the developer of this "firstclass" app and obtain from them instructions for installing/using it on your specific BB device model and OS level. If they have not written their app for BB10, then it's not available...but they remain your resource regarding if/when it shall ever be.
Occam's Razor nearly always applies when troubleshooting technology issues!
New to the Community? Click here and also here for helpful guidance. Also please click here for additional helpful information to guide you as you proceed. I always recommend that you treat your BlackBerry like any other computing device, including using a regular backup schedule...click here for an article with instructions. If anyone has been helpful to you, please show your appreciation by clicking the button. Need a reference to BB10 OS/SR versions? Click here. Need a specific BB10 AutoLoader? Send me a private message.