I can't install my app (.apk) on my android device

I build it on Unity3D. This application has open,read and write file.
I copy it to galaxy tab 10.1 (2014 edition) sd card and touch icon to install but I can’t touch install button.
My tab show this pop up

I can touch only Cancel button. If I touch install, nothing happen and this pop up still show on my tab.
Please help me, I want to know how to install my app or what is wrong?

One way to install the apk from your PC is by using the adb tool, which is located in the platform-tools folder, inside the Android SDK folder, e.g.:

C:/Program Files (x86)/Android/sdk/platform-tools/adb.exe

If you set the “Path” environment variable to the above folder, it will make things a lot easier. You will be able to run"adb" from the folder where your apk is located:

You should also enable “USB Debugging” in your device. I’m not sure the exact path for the galaxy tab 10.1, but for my device it’s:

Settings/Applications/Development/USB Debugging

It should be something similar for you too.

After you’ve done the above, connect your device with a USB cable to your computer and open a Command Prompt window. Inside the Command Prompt window change the current directory to the directory where your apk is located:

After you get to the correct directory, run the following command (assuming you have correctly set the PATH variable):

adb devices [and press Enter]

This command should start the adb server if it’s not already running, and it’s output will show you your device ID.

Then type the following command:

adb install “your File Name.apk” [and press Enter]

The installation will start, and hopefully will finish with adb output “Success”.

Disable your screen dimmer and try again.

-Make