Installing a custom ROM on a BlackBerry Passport is not a standard software-only process. Because the device uses a locked bootloader (QNX-based BB10 OS), modern custom ROMs like LineageOS require significant hardware modification 1. The "Android Conversion" Method
Disclaimer: I am not responsible for bricking your $800 paperweight.
While there is no "easy" way, two main paths exist for modding the Passport:
Once the installation is complete, follow the on-screen instructions to configure your device and restore your data.