To open an app, swipe up from the bottom of your home screen, then touch the app.
You don't need to close apps. Android manages the memory and battery that apps use, so you don't need to worry about leaving apps open.
To close one app, tap 
To close all apps, touch 
Touch 
Or, if you're using gesture navigation, drag up from the bottom of the home screen, hold, then let go.
In your list of recent apps:

To search this help, tap 
If you don’t see what you’re looking for, check for app-specific help:

