Our textbook covers three hardware description languages: Verilog, VHDL, and SystemVerilog. As a result, the book's sections on these languages (Sections 3.9, 3.10, 4.12, 4.13, 4.14, 4.15, 5.6, 6.6) might confuse you.
The only language we'll use is VHDL. You can find many VHDL tutorial on the Web. Listed here are some that I think you'll find useful.