Once installed the app does not need to be started. Just swiping the YubiKey NEO against the phones NFC reader will cause it to run, displaying a message to indicate that the OTP has been copied, all without leaving the currently running app.
Note that the default NDEF programming needs to be used. If you've reprogrammed the NDEF tag of your YubiKey NEO, you will need to change it back to the URL: my.yubico.com/neo/
This can be done using the personalization tool: opensource.yubico.com/yubikey-personalization-gui/
When using a YubiKey NEO with a static password in scan code mode you will need to configure which keyboard layout to use in the YubiClip Settings. Currently only the US layout is supported. If you would like to see additional layout support, please consider contributing code via a pull request to our source code repositiory: github.com/Yubico/yubiclip-android/