First, make sure you have ADB, if not. you can get it here.
After that, unzip the folder and go into it.
While holding "Shift", "Right Click" with your mouse, and press "Open PowerShell Window Here"
You should be at a powershell window now, type "./adb devices and press enter.
if all goes well you should see this.
Enable Developer Settings on your Android Device by following this. (not gonna bother explaining it xD)in Developer Options, Enable "USB Debuging" and Plug your Device into your computer.
Type "./adb devices again, and your device should show.
put a .apk file in the same folder as the ADB folder.
In powershell type "./adb installxxxx.apk (xxxx is the apk file name)