1.Your device must have Custom recovery to install CM13 rom.
2.Make sure to have About 60% battery before starting.
3.Always make backup or current rom and your data.
So lets start the guide on How to install Cm13 rom in mi3w by custom recovery.Follow below step by step guide.
#How To Install CM13 Rom in Xiaomi MI3W
2.Now paste both the file in your device memory and reboot your device in too recovery.
3.After rebooting to recovery flash CM13 rom from it and then flash Gapps6.0.zip.
4.Clear cache,Data and Factory reset your device
5.Now reboot your device done!
6.Enjoys Android marshmallow 6.0 in your Xiaomi mi3w.