Remember, atacs is the center of our universe. Layout A design may begin with an HDL like VHDL or Verilog. Atacs can chew VHDL from here. Piece of cake. The more interesting case is when a design begins as a schematic.
Schematics contain blocks or symbols that describe behavior.
Also, I will only attempt to describe the bare minimum of steps necessary to accomplish a given task. Feel free to toy with other parameters and options that are available on many of the dialog boxes. You are now ready to edit a schematic. Otherwise, it is necessary to create components with VHDL behavior views. Creating components can be done in a variety of ways.