The android tool is located in the tools directory in your SDK. You need to add this to your PATH environment variable so that bash can recognize it.
You can do this by adding it to your PATH in your .bash_profile file. This file should be located in your home directory. Create if it doesn’t exist using vi .bash_profile and add the following line to it:
export PATH=<path_to_android_sdk>/platform-tools:<path_to_android_sdk>/tools:$PATH
where <path_to_android_sdk> is to be replaced with the path to your SDK. For example: "/Users/me/android-sdk-mac_86/platform-tools"