There is a shell variable called path. This is a list of
the directories that Unix looks into to find an executable program when
you type a command. If a program is located in a directory which is not
on your path, then Unix will be unable to find it and the program cannot
be run. A new command must be placed in a search path of the shell. For
example, howmany may be placed in the directory bin
and this directory can be added to the shell's search path with the command,
% set path=($path ~/bin)
Note, $path stands for the current value of the shell variable
path and ensures that your existing search paths are not lost! The ~
character in front of /bin is a shorthand way of inserting
the user's full home directory to distinguish between the system /bin
directory.
This may be best placed in the .cshrc file