You will need the platform-tools from the Android SDK on your computer. Download the platform-tools as per your operating system.
Windows users will need proper drivers installed on their computer. You can try the simple FWUL adb/fastboot ISO or the Naked ADB drivers or the Universal ADB drivers if you don't already have a working driver installed Download the correct image file and copy the file into the same folder as your platform-tools as well as device's storage. Rename the image to twrp.img. Now reboot to fastboot/bootloader mode by using adb or manual key combos (Use Google to find that if you are not sure). To use adb to reboot, use the following command:adb reboot bootloader
Flash the downloaded image using the following command:
fastboot flash boot twrp.img
Reboot to recovery (you can use key combinations also)
fastboot reboot recovery
Preferred Installation Method:
Once booted, put your stock boot image in Internalstorage , MicroSdcard or Usb-Otg then Flash stock boot image in boot partition and tick (Flash to both slots) , after that navigate to the Advanced > Flash Current TWRP option. This will install the TWRP image you just booted permanently to the device.