Before all, I am not responsible if your device get bricked or something like this.
So you need to unlock the bootloader before, check this tutorial to do that : http://forum.xda-developers.com/meiz...pro-5-t3303127
After that, download the twrp image here : http://forum.xda-developers.com/meiz...-pro5-t3349888
Then place the twrp file on your desktop.
Boot you Pro 5 into fastboot mode (Power+Vol down) and connect it to pc.
Launch cmd, and then go to your desktop :
Then type this command :
fastboot flash recovery twrp_pro5.img
And that's all, now you can boot on TWRP with Power+Vol Up