Waiting on that awesome +1 button in your Android market? Need to lock access to your market down to keep people from buying/installing or uninstalling apps? If you haven’t gotten the latest update yet, you can manually install it by downloading the APK file (here) and installing it like you would any third party app. Be sure to have Unknown/Third-Party Sources enabled in Settings > Applications. We’re aware that some of you haven’t even gotten the first update (the one that first introduced the UI changes). No use in waiting, really – these are all the same APK files that users would otherwise get over-the-air. Your phone won’t explode into nothingness if you install it. And you don’t need to be rooted. Get to it!
SOURCE: Download: Phone Android Market 3.1.3 Adds +1 For Apps And Games, PIN Number For Purchases, And More