The Tecno J8 is an MT6753 powered phone running on Android 5.1 (Lollipop). If for some unknown reasons kingroot apk is unable to root your Tecno J8, then you can root using the procedure below
Copy the TWRP recovery.bin and scatter file from the TWRP zip file downloaded above into the Hovatek folder, making peloader.bin, scatter file and recovery.bin (TWRP) in the folder