Open Settings
Tap System
Tap Languages & input
Tap On-screen keyboard
Tap Default keyboard
Select the keyboard you want to use
Open any app with a text field
Tap the keyboard icon in the navigation bar or notification area if needed
Choose your preferred keyboard from the list
If the keyboard is not installed, open the Play Store
Search for the keyboard app
Install it
Return to Default keyboard and select it
Grant any required permissions if prompted