how to install img(firmware) file to android device from sd card?

my android device Vtouch v705 tablet has been pattern locked so i tried to hard format but it doesn't worked for me(system hanging) no way to work resetting key

i have its firmware(img file) but i dont know how to install this firmware at this circumstance
lots of programs available but every program needs to ON Usb Debugging mode in this case not possible
is to possible to update firmware/flash the device from sd card
note that gmail login and resetting keys both didn't work
please give me good solution to bypass the such a problem
thanks......