Follow few simple steps shown as below to lock apps on Android:-
Step 1: To lock Apps on Android, download & Install “App Lock” App from Google play store on Visit Here.
Step 2: Once the app gets successfully downloaded and installed the icon will be shown on your home screen.
Step 3: Open the app and you will see some steps to follow, in the first step you have to draw, your unlock pattern for android app lock.
Step 4: Then in the second step, you have to confirm your pattern, finally, in the third step you have to enter your security email, then click on the save button.
Step 5: Select the app which you want to lock, once you click on the app it will ask you for the permission.
Step 6: Simply you have to grant the permission to lock your app and your app gets locked.
In this way, your app can lock on android.