You need to activate the Developer Options and USB Debugging for the purpose. Follow the below mention steps and you would be good to go:

1.Slide into you Settings > About > Kernel Version.

2.Tap on it Multiple Times and this will grant you the position of a Developer.

3.Go into Settings > About Phone > Developer Options and tap on USB Debugging

4.Now all you have to do is turn ON the Fastboot mode and use the Bootloader.

5.Install recovery for Flashing and find a supporting Custom ROM.