D-Link D DPH-50U DPH-50U Quick User Manual page 8

You will see the End User License Agreement. Click the "I have read ..."
checkbox and press the I Agree button as shown below.
You will see the following progress bar below indicating that the installation is
proceeding.
Wait until you see the following popup and press the OK button.
Connect the USB cable to the D-Link VoIP USB Phone Adapter USB port as
shown below: