Download the LineageOS 14.1 Xiaomi Mi4/Mi3wThere are only two version availabe, experimentals build and nightly build. But don't worry, this custom rom surely will get the stable release after beta stage :D aw... How long is that? Who knows..
Now you can proceed for flashing with your already have custom recovery. Do this with cautious, don't recklesly flash it to your Mi4 and Mi3w. Or you can follow the tutorial How to Install LineageOS for Mi4/Mi3w it is the same step except the rom zip file. Wooohooo... Beat that broo.. Recomended reading : Enable Native Root on Lineage OS or replace it with SuperSu