I will describe a few simple steps to perform a hard reset on the Lenovo A390t:
1) Turn off the device if it is turned on.
2) Press the volume button up and the power button simultaneously, wait for the Recovery menu to appear.
3) In the recovery menu, press the volume down/up button to highlight “Wipe data/factory reset” and select it by pressing the power button, then select “Wipe cache partion” in the same way.
4) When cleaning is complete, the recovery menu will appear again, in which we select “reboot system now“, after which the device will reboot.
Done.