This is a simple process that allows you to install applications in APK format. Either you have downloaded them from another website or if you are testing an application in development.
Follow these steps:
- Go to Settings
- Select Privacy
- Now go to Additional Settings
- Select the option Allow Installation from Unknown Sources
- On the next screen you must select the application through which you are downloading the APK file. Usually this is done through WhatsApp or Google Chrome.
In the list that appears, choose the application with which you are downloading. - Once the app is selected, activate the checkmark that says Allow from this source
And voila, you can exit the settings and retry downloading the app.
EN 
ES_ES