Android Studio 0.4.2 is now the current version in the Android Studio dev channel. To install this version manually from .zip files, see the 0.4.2 build page for download links.
To update your dev-channel build from the previous version (0.3.2) to the current version (0.4.2) you need to make two edits to your project.
For information on how to do this, see the description and images in the release announcement for 0.4.2 when it hit the Alpha channel. Note that after updating the version in your build.gradle file, either restart the IDE or press the gradle sync button in the IDE toolbar.