To enable the manual installation of an application, you must first enable applications from unknown sources (see the How do I install applications that are not in the Play Store? FAQ). Next, you must make sure that the installer is an .apk file, as this is the only file type that can be installed on the Android OS.
After you have downloaded the installation file to your computer, use the micro USB cable to connect the device to your computer. When prompted, choose Disk drive as the connection type on your device. On your computer, go to the newly mounted Removable Disk and then copy the file to the microSD card. Once the transfer is finished, disconnect your device from your computer.
In order for you to be able to access the file and install it on your device, you will need a file manager application installed. From the Home screen, tap the All apps button, tap Play Store and search for the keyword “file manager.” Locate and download a file manager application.
Using your file manager, open the folder where you copied the file. Tap the installation file then tap Install. Once the application is installed, it will be available in your All apps menu.