How do I loosen the tension on the hinges? The PDF gives no information.

Instructions are on back of package. Here the instructions. Using the provided hex wrench key, insert short end of wrench into the hole at the top of the hinge barrel. To disengage the inside locking mechanism, apply a downward force. The wrench will sink about an eighth of an inch, holding that downward force turn the key counterclockwise to release the tension. To tighten spring follow same steps but now turn the hex key clockwise.