To activate your card online:

Log in to your Payoneer Account.
Once you have logged in, you will see a drop-down menu at the top of the screen listing the Payoneer Cards for your account. Please make sure that the correct card is selected by confirming the last 4 digits of the card number.  
Click on "To view your status and activate your card Click Here!"
Follow the on-screen instructions to activate your card.
To activate your card via telephone:

Call the phone activation service at 1-888-802-4442 (within the US) or 1-646-658-3695, Ex-3 (International).

You can view the steps in this video.