==> Unzip the TWRP zip file and flash the recovery image to the phone using SP Flash tool ( You can download SP Flashtool here)
How Can I Flash it Using SP Flashtool? Please see guide here
==>Boot the phone into TWRP recovery mode (by Holding the Vol Up and Power button for 5 seconds)
==>In TWRP recovery, Choose install zip from sdcard- to Choose zip from sdcard use vol up and down scroll up and down then choose the Supersu.zip file from the root of your sdcard.
Scroll to yes and install, after a successful flashing, go back and reboot.
You are now rooted! To be fully sure your Tecno Phantom 5 is rooted, go straight to Google Playstore and downloadroot checker to verify your root status.