DE2-115 complete beginners question

I think you have to download from the Altera website:

1) Quartus (web editon) free

2) Modelsim Altera Starter edition (free)

3) In the installation directory of Quartus youll' find the 'USB blaster' drivers.

This is all you need to design a circuit and download it on the FPGA board.

P.S. You also need the knoledge of a language such as VHDL or Verilog. This is not a must since you can also design using the schematic design (similar to Spice) but it becomes immediately very cumbersome as the design complexity increases.