Using a Parkour Park - Your Training ground
Parkour parks are public areas designed for the training of Parkour by everyone, therefore the first thing to note might be that you will be sharing this spot with others. This is a lot easier if you break the ice and talk to them at least to negotiate which direction/area you want to move in to save any unwanted accidents.
Break the ice
Quite frequently children use these parks, even though technically it is meant for adolescents and above, so it is well worth being a good role model while training and speaking with respect if you would like to use a specific area that they are using.
Drill the basics
Navigating a purpose built spot is a really good way of working on many different techniques without the risk of being "kicked off". At a Parkour park most of the fundamental techniques can be practiced and built up to, a good example of this is swinging movement which is usually quite hard to find in the urban environment. This leads to a lack of experience so when a spot is found with a swinging movement it is unlikely the practitioner will be competent enough to perform it or even train it with correct technique.
A Pk park lets you train straight from a beginner level allowing a technique to be learned without dire consequence and then progressed to competency so then it can be applied with minimal risk at an actual spot.
These facilities are great for both solo training and group sessions, allowing practitioners to share ideas and learn from each other's experiences with Parkour. As stated above moves can be isolated and applied many ways within the park to progress them, alternatively routes can be set that test many moves that flow together to achieve better route setting and execution.
When training partners get involved this becomes a lot more interesting as everyone sees different routes and options within those routes. So if you train in pairs or groups the likelihood of you learning new movements or ways of solving problems is increased immediately when you communicate about what you are trying or have done before.
Have some fun
Fun games to play with training partners or on your own are to set routes that eliminate certain obstacles from being allowed to be used. A good example of this is the game Floor Is Lava which instantly creates a fun challenge to keep off the floor when deciding which way to move.
Depending on the setup of the park eliminating Poles or Walls when setting routes can also create fun problem's to be solved by you toolset of movements. Along with route setting challenges come more group intensive games like Parkour Tag which rely on the standard rules of tag with a bunch of obstacles to use to put distance between the evader and chaser.
It's gonna hurt... a little bit
Last note about Parkour parks and their uses; as mentioned above swinging can be quite unique at Parkour spots and the parks usually make up for this by including many bars to swing from in their design, although this is great to utilise a skill set that has been neglected it also leads to the consequence of that neglection, namely "Rips". A rip is when the friction from swinging cause the skin on the hand to form a blister, then if continuing to enjoy swinging through the pain they will rip causing a few layer deep hole in your hand. Don't panic! This will heal and form a strong part of skin to replace it, a callus, that which will be able to endure more swings than before given the right time to heal and strengthen.
These are inevitable when swinging a lot, my advice is to notice when you form the blister and then keep off them hands. Once the blister has gone down or popped (usually a few days) then make sure the wound is clean and rest it further until there is a layer of protective skin formed and strong enough to bear your weight. Then you may continue monkeying about with your new improved hands.
Good luck and be safe out there