Before you can use the program, which takes a query, retrieves matching references and generates a bibliography, you must write a bibliography file, whose format is described here.
Click here for guidance on actually running the program.
Click here for troubleshooting.
When you first install REF, you need to modify line 27 of the program to set up the path of the directory you want REF to work in (this directory is where REF will look for input bibliography files, and where it will output the bibliography file it generates, ref-output.html).