You can use the code below to install application from command line
adb install example.apk
this apk is installed in the internal memory of current opened emulator.
adb install -s example.apk
this apk is installed in the sd-card of current opened emulator.
You can also install an apk to specific device in connected device list to the adb.
adb -s emulator-5554 install myapp.apk
Refer also to adb help for other options.