dos version, c program

[beginner]

Gentlemen,
someone gave me a program made in C language, in MSDOS environment. it is an old program and he wants to modify it. I made research over the internet and found "codeblock" as an editor. now when I am trying to create a new project and add the files that I have, nothing except "GNU compiler" is working. but I need to use something for dos environment, because there are dos libraries inside.
when I try to create a new project with "C++ compiler" or "tiny C compiler" or anything else, it is saying that the environment is not set.
could someone please help me to set the environment for "Borland C++" for example? or anything compatible with language C on dos environment?
thank you very much

[oBFusCATed]

Have you read this http://wiki.codeblocks.org/index.php/Installing_a_supported_compiler ?