Before you can connect your phone and your vx660 terminal you need to set up wifi in the terminal. You'll need to follow this process any time you change phones or if you reset network settings in your phone.
Press and hold the green/enter and 1 buttons at the same time and then press red/cancel. On your phone enter control centre and enable hotspot (See Turning on hotspot).
Next, you'll need to tap Menu > Down arrow > Utility > Down arrow > Network > WIFI. Tap scan new to have the terminal discover the WIFI network exposed by the Personal Hotspot on your phone.
Once you find your phone, tap on it and enter the password that you set earlier (See Preparing your phone for Hotspot).
Once connected tap any button followed by the red/cancel button.