You can build from scratch using javac or just run the makefile with make. You have the following options:
make: which will compile the program and create a .class filemake run: which will compile and automatically run the program with all required arguments (RECOMMENDED)make clean: which will clean up any build files (just .class in this case)
Note: after unzipping the main folder, you may have to run:
chmod +w project: if the permission to write does not already exist