Root Redmi 3S/Prime Via TWRP

Step before Rooting Redmi 3S/Prime Via TWRP :

Read : Install TWRP on Redmi 3S/Prime Via Fastboot

-Enable Developer Option. Go to Settings> About Phone> Touch MIUI Version up to 8x, until a pop-up "Now You are a Developer"
- Go to Developer Options> Enable USB Debugging
- Download SuperSU V2.78

Step to Root Redmi 3S/Prime Via TWRP:

1. Move SuperSU (Do not extracted) to internal storage ---> folder download
2. turn off redmi 3S / Prime, enter TWRP Recovery (Vol Up + Vol Down + Power) simultaneously
3. Click install -> internal storage -> download folder ---> click SuperSU that you have downloaded ->  swipe to confirm flash wait for it to finish.
4. reboot the system
5. done
You can check with the root checker application from Google Play.

Root Redmi 3S/Prime Via TWRP