Are you looking to sign up to Wonder PRO? Here's how:
Go into your Wonder space for whom you would like to sign up for PRO seats and enter the menu (icon in the lower left corner). You should now see the "Subscribe to Wonder" button (see screenshot)
Next, select the number of PRO seats you would like to sign up for. Note that the minimum number is 3 and depending on your location, the price and currency may differ. Once selected, click "Activate Pro!"
Now enter your email address and press "Continue"
Enter your location and press "Continue"
You can either pay with PayPal or with a Credit Card. At this point you can also enter a Coupon code (just click "Add Coupon").
Enter your payment information and click "Subscribe Now", that's it!