The release folder contains a Windows excecutable in the build directory. There are also Mac, Linux, and web versions available, each in a separate directory. When the game starts from an excecutable, there are options for graphics settings and resolution. If the framelate is low, try setting the graphics to simple.
Once the game starts, one player should press the "Start Server" button in the top right corner of the screen, followed by the "gamejam" button in the lower left corner. Other players can then connect to the server through LAN.