If you start using a new Google account on your Android device and you own apps that are tied to another Google Play account, you may want to transfer those apps to your new account.
Unfortunately, there is no way to actually move apps from one account to another. Even if you contact Google about it, they will not be able to help you. However, you can add the old account to your Android and install any of the apps on both accounts. Just use these steps.
Note: These steps assume you are already running your Android device that is already tied to the newer Google account you are using.
1. Open Settings > Accounts. (Menu may be differently worded depending on version of the Android OS or device)
2. Select Add account.
3. Select Google, then go through the steps to sign your Android into the old account.
4. Once finished, you can access the apps tied to the old account by opening the Google Play app and selecting Menu > Accounts. Choose the other account and you can install any of the apps listed as well as utilize any of the music or books tied to the account.