I FINALLY figured it out since there was nothing on the website:
(1) Go to your calendar and you'll see blocked dates in grey.
(2) Click on the grey date you want to make available and DRAG to either the end of the month or the last day you want unblocked. DON'T TRY AND DO THIS USING THE BOXES ON THE RIGHT - THEY DON'T WORK!
(3) Click on the "Available" box on the right instead of the blocked box. This will unblock those dates.
For multiple months, you have to go through each month from the 1st to the end of the month... drag to the end of the month... click "Available". You have to do this for every month.