DSOL is an open source suite and as such published on the open TU Delft SVN. A download can be obtained from https://simulation.tudelft.nl/dsol/3.0/.
In the tutorial section, a number of examples can be run out of the box. Play around with the different windows, see the animation, and experience what DSOL can do for simulation studies! In order to run the 2D/3D animation examples, you'll have to install Java's 3D libraries which you can download from Oracle.
After running the web-based tutorial examples, the next task is to see how to develop models. The maven instructions indicate how to include DSOL in your project.
Now it is time to read the tutorial and understand the concepts, design guidelines and language constructs. Have fun and don't forget that DSOL is based on the idea of an open source community. Your feedback, questions and experiences are more than welcome!