1 - Boot your device into fastboot mode:
      adb reboot bootloader     (or power off and power on again
      while pressing Power + Vol Down)
2 - Flash LineageOS recovery via fastboot
      fastboot flash boot <name of the file>
3 - Reboot to recovery
4 - Perform factory reset (formatting data is important)
5 - Here you have 2 choices to install rom
      1) Apply update > apply from ADB
          on PC open terminal and type - adb sideload <rom zip name>
      2) Apply update > install from sdcard
          Just copy rom to the sdcard and install it.
6 - Reboot to system, wait until rom booted, then reboot
     in recovery again.
7 - Now you can install other zips (gapps, magisk etc) if needed by
     using the methods described in the 5'th line of guide.
8 - (IMPORTANT!)If you flashed gapps, factory reset once more is required.

* For new Magisk versions change file extension to zip to be able to
   flash it.
* This guide is based on Lineage OS recovery.
* Not recommended to use any other custom recoveries on fw11
   based roms, it can cause issues for the phone.