Trying to flash a custom rom into Nexus 7 2012.

First step : install ABD.

Copied from : http://stackoverflow.com/questions/31374085/installing-adb-on-mac-os-x

Option 2 – Manually

1. Delete your old installation (optional)

   rm -rf ~/.android-sdk-macosx/

2. Download the Mac SDK Tools from the Android developer site under “Get just the command line tools”
3. Go to your Downloads folder

   cd ~/Downloads/

4. Unzip the tools you downloaded

   unzip android-sdk*.zip

5. Move them somewhere you won’t accidentally delete them

   mv android-sdk-macosx/ ~/.android-sdk-macosx

6. Run the SDK Manager

   sh ~/.android-sdk-macosx/tools/android

7. Uncheck everything but Android SDK Platform-tools (optional)
8. Click Install Packages, accept licenses, click Install. Close the SDK Manager window.
9. Add platform-tools to your path

   echo 'export PATH=$PATH:~/.android-sdk-macosx/platform-tools/' >> ~/.bash_profile

10. Refresh your bash profile (or restart your terminal app)

    source ~/.bash_profile

11. Start using adb

    adb devices

adb push filename.zip /sdcard/