Similar to how an android ROM is being flashed, you can also flash Google apps, gapps in similar way.
How to Flash Google Apps, Gapps On Android
1- First, you have to download the gapps package that corresponds to the version of android on which you are flashing the gapps. E.g, if the android version of your phone is currently android 4.2.2, you need to flash the exact gapps package for that android version.
2- Put the gapps package on the root of your SD Card thus, directly on the SD Card and not in any folder of the SD Card.
3- Now, boot the phone into the recovery mode. You can boot the phone into the recovery mode by using the recovery short cuts (combination of buttons) or using the command prompt command line; adb reboot recovery (does not work for all android devices).
4- Once in the recovery, you do not need to wipe any partition. Just select the "Install Zip from SD Card" option then; "Choose zip from SD Card".
5- Confirm that you want to flash the gapps package and wait patiently until the process completes then; reboot your phone.
You must have a custom recovery like 4ext, ClockWorkMod, TeamWIN recovery flashed on your phone before you can be able to flash any gapps package.
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