Manipuri Keyboard APP
Go to your device Settings.
Go to Languages and input.
Now choose and select "Meitei Mayek Keyboard".
The steps might vary depending on your device, so follow the steps for your device and choose the appropriate options to change the keyboard.
For eg. for Samsung Galaxy J7 pro with Android 9:
Navigate to:
Settings -> General Management -> Language and input -> On-screen keyboard -> Manage keyboards
Then turn on the switch for "Meitei Mayek Keyboard", then navigate back to "Language and input" -> "Default keyboard"
Now select "Meitei Mayek Keyboard" from the pop-up menu.
Now you can start typing using this keyboard.