Nowadays Ab-initio quantum chemistry methods have been used widely, not just to explain experimental data but also to predict it. Basically, these methods attempt to solve the many-body Schrödinger equation to obtain any molecular properties. Many computer programs built to carry this purpose.

Today, anyone can practice quantum chemistry.

Developed by Mark Gordon's Quantum Theory Group, GAMESS (General Atomic and Molecular Electronic Structure System) is one of them. This program has a wide range of capabilities in quantum chemistry methods and a very active community forum. Plus, it is a "site license at no cost" program. This means you can get it at no cost. If you are a student that just studying quantum chemistry than it is a perfect choice for you. If you are a researcher, it should also good for you.

Here are some steps to get the program on your computer system.

1. (Optional) Go to GAMESS source code distribution page. The page gives information about GAMESS source code for your computer system.
2. To get the source code, you should agree to GAMESS User License Agreement.
3. After choosing to agree to the license agreement, you will be directed to GAMESS Registration System. Fill your email address there.
4. Now you can choose GAMESS version based on your computer system. If you are not sure which one to choose, you actually can choose all of them then decide later which one to install on your system.
5. Wait until they send you link and password to get your program.
6. On the download page, don't forget to also download the directions file, which contains complete instructions to install it. They made the instruction so details and easy that even a ten years old kid can follow.

Tadaaa, you have it now. Shall we begin???