The Google Play Store app, formerly branded Android Market, typically comes preinstalled on all Android-powered device's running anything above Froyo 2.2. Google doesn't supply a copy of the Play Store app for download, so if you're using a supported HTC device and don't appear to have the app installed, you'll need to undertake a little detective work and troubleshooting.
Check Google's website to find out if your HTC handset is supported for use with Google Play. If your device isn't on the list, consider upgrading if you want to download content from Google's mobile store.
Search through your apps to make sure you don't already have Google Play installed on your handset. Google Play is typically preinstalled on the home screen of Android devices, but you or somebody else may have inadvertently moved the app to another location on your phone. Tap the "Apps" icon on your home screen to search through your currently installed apps.
Update Android. If you're running an older version of Google's OS that doesn't support Google Play. You'll typically need to enter your device's "Settings" menu, scroll down to and select "About device" and hit "Software update," although the precise method will depend on the version of Android you're currently running. The Google Play Store app will be installed on your phone if an appropriate update is available for your HTC device.
Reboot your device while connected to a strong Wi-Fi signal to see if the Google Play Store app appears on your screen. If it does not and you're using a supported handset with an up-to-date version of Android, Google recommends contacting HTC or your network provider for advice.
Back up your data and restore your handset to its factory settings if you've deleted the Google Play Store or are experiencing other problems with your device. You'll need to link your handset to a Google account and access backup and restore options through the "Personal" section of your "Settings" menu, although this may vary depending on the version of Android you're running.