Follow the instructions there to install Mesos on your system (be it a live, physical box or a development VM) and start experimenting with it!
The new release delivers the new HTTP API for Frameworks, among a bunch of other exciting features (for example, support for Permanent Storage and reserve/unreserve endpoints) and I highly recommend that you play with it (I will be presenting a Tech Lab at MesosCon Europe where I’ll show how easy it is to write a Ptyhon framework that used the API to launch tasks and containers).
If you want to experiment with it on a dev environment, Vagrant may be the fastest way to get up and running: I have created a simple Vagrantfile that sets up a Master/Agent 2-node setup.
This still needs some refinement, but it’s good to get going and experimenting: please do let me know if you find ways to improve on that (Pull Requests welcome!).