Install an apk file from command prompt?

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.

Use the Android Debug Bridge command line tool adb eg: adb install filename.apk.

A good reference for adb is Here

install [options] <PATH>    Installs a package (specified by <PATH>) to the system.
Options:

-l: Install the package with forward lock.
-r: Reinstall an exisiting app, keeping its data.
-t: Allow test APKs to be installed.
-i <INSTALLER_PACKAGE_NAME>: Specify the installer package name.
-s: Install package on the shared mass storage (such as sdcard).
-f: Install package on the internal system memory.
-d: Allow version code downgrade.
uninstall [options] <PACKAGE>   Removes a package from the system.
Options:

-k: Keep the data and cache directories around after package removal.

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.