There are two common ways to access System settings. The quickest way is if your device has a menu button, just press it while on the home screen, and then tap System Settings. The other way to load settings it to open the Settings app from the app drawer. In the settings menu tap the Apps button.

Now the device should be displaying the apps list. From here tap the menu button again and then select “Reset app preferences.” The reset app preferences button will appear, just tap Reset apps. This will:

Reset any disabled appsReset app notification settingsReset all default application preferencesReset background data restrictions for apps

The change will happen in the background, and it should be done instantly.

Now all of your default app file associations will be reset and you can select new ones when you an execute an action that could possibly open in multiple apps.