Why I can't install apps on my phone (With Picture)

Just follow the below instruction hopefully your problem will solve.

Step-1: First of all click an app like below picture :)

Step-2: Then you will show like this interface click the 'Settings' button :)

Step-3: Again click the 'OK' button :)

Step-4: Select 'Unknown sources' checkbox option :)

Step-5: After clicking this option you will show like below interface :)

Step-6: This is final step now  go to your apps folder click an app, you will show install option :)

Thank Yor for Reading