What is a .ins file and how do I compile it?

The manual installation of the class and bibliographic styles involves running the file cjs-rcs-article.ins through LaTeX.

By convention, a .ins file is a batch file used to install a LaTeX package. To run the program, you provide it as input to any TeX engine. For example, from the command line:

latex cjs-rcs-article.ins

Most LaTeX editors will let you open a .ins file and compile it from their interface as you would any other .tex file.