You can send data in your tree to another player by right-clicking on it and selecting "Send to player". If you do that for a container node it sends everything underneath it too.

Now currently the data is not shared in the sense that an edit to one player's copy will NOT change another player's copy of the same data. That's a feature we hope to add at some point. If there is a bug or something in a player's data they can send it to you (a copy that is) and you can check it out, fix it and send it back - another copy.

The most important piece of data that changes in D&D is your HP. There are a couple of ways to transmit this data in an easy way in the absence of "shared data". The most popular is probably to the Game Status Controller plugin.

Plugins add effects to the basic openrpg software and there are a fair few of them you should look over. In the plugin list there's a button to press to give you a brief description of what they do when you have a plugin selected in the list.