As you have seen above, MIRIAD programs are just Unix programs that you can run, normally from an interactive shell, or through a shell script. The other thing to re-emphasize is that most MIRIAD datasets are implemented as a set of items (usually files) organized in a directory. You refer to a MIRIAD dataset by its directory name, you can use the tools on your computer to copy, rename, remove, archive etc. them.
If you need help on a MIRIAD command, there are several ways. For example for uvcat you would type:
mirhelp uvcat uvcat -k uvcat -kw
Appendix B contains another quick summary of MIRIAD and some of the options you will frequently use. Appendix E lists the peculiarities of the MIRIAD data dialect that the CARMA telescopes write, which can be useful for those familiar with MIRIAD data from other telescopes.