it will install a GitHub and a Git Shell
    GitHub is mainly used to visualize change history
    Git Shell is for version control and changes submit

    by clicking "Clone in Desktop" button at the lower right corner on page 
        https://github.com/SM-at-THU/StatisticalMechanics
    or by clicking "+" button at the upper left corner on GitHub Desktop, then
        choose "SM-at-THU"(it should appear if you accept the invitation successfully), "clone", "StatisticalMechanics" and finally "Clone repository"(at the bottom)
        
    in both way GitHub Desktop will ask you to browse a path for you to put the clone of StatisticalMechanics.
        default path(C:\Users\<your account>\Documents\GitHub) is suggested

Although GitHub Desktop offers functions such as publish and synchronize, they are not clear enough. 
Sometimes you modified your file and clicked "sync" in GitHub Desktop, but the file remains unchanged on the GitHub website. So we need Git Shell.

Introduction to some Git commands:

    (http://blog.csdn.net/chun799/article/details/9095635)
    
Only commands listed below are usually needed:

            git status
            
    to check modified files, files not change and files Git didn't track
    There are usually three kinds of file status:
        Changes to be committed: files whose changes will be uploaded
        Changes not staged for commit: files changed but won't be uploaded
        Untracked files: files which Git didn't track their changes

            git add <foldername or filename>
            
    to add folders and files from "Untracked files" and "Changes not staged for commit"
        to "Changes to be committed"
    you can use "*" for abbreviate, e.g., git add class* will add all folders and files whose name begin with "class" 

            git commit -m "<some notes here>"
            
    to commit changes of files which are in "Changes to be committed"
    Be aware that after this command the changes is still local

            git push
            
    to submit your local changes online
    things on (https://github.com/SMTMSbyMET/smtms) should change now

    to get changes from website to your local repository
    better to use git status to check changes first