Now that we've discussed VHDL itself, it's time to learn the development environment. If you don't already have it installed, you will want to install the [http://www.xilinx.com/ise/logic_design_prod/webpack.htm Xilinx ISE WebPACK]. The ISE Foundation is a professional tool that will cost you an arm and a leg. The ISE WebPACK is a free version of the software that does most of what you need (unless you have large, complex designs or are working with the newest and best Xilinx FPGAs). Once you've got that installed, fire it up.