Removing unwanted apps
Every app that exists on your device is a potential privacy and security problem. Google automatically grants every app permission to use the Internet, including unwanted apps. This means that every single app on your device can:
Send any data it can get its hands on to points unknown somewhere on the Internet
Receive all kinds of things from the Internet that could affect your device
Removing third party apps
Go to Settings -> Apps. You should see a list of the apps on your device.
Tap an app you do not absolutely need to have on your device.
At the bottom, tap Uninstall. Then OK to uninstall the app.
Repeat for each app you can do without.