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.
You can build on the command line with ant. See this guide.
Then, you can install it by using adb on the command line.
adb install -r MyApp.apk
The -r flag is to replace the existing application.