- Download the file on your phone or move it there from your computer.
- Reboot your phone to #dic:recoverymode
- Perform a #dic:hardreset
- Install the file via recovery mode.
PS: Sorry, since I never used the standard Android recovery I forgot to mention that you need TWRP first. So, as @Paule says it’s best to install FP Open first (Thanks for the hint @Sietse).