I read the Replicant installation guide, but it's kind of difficult. I already have TWRP installed on my device, so I'm going to use that to install Replicant. Can't install it?
Yes, you can use TWRP. Just put the zip file of the system image somewhere accessible by TWRP (sdcard or internal memory). Then ask TWRP to install that zip. Also, better clean your data and cache partitions before that.