The following installation instruction is for unix although the package should work as well with any other operating system.
To install the SymbCompCC package, unpack the archive file, which  should
have a name of the form SymbCompCC-XXX.tar.bz2 for some version number 
XXX, by typing
bunzip2 SymbCompCC-XXX.tar.bz2
tar -xvf SymbCompCC-XXX.tar
in the pkg directory of your version of GAP 4,  or  in  a  directory
named pkg (e.g. in your home directory). (The only essential difference
with installing SymbCompCC in a pkg directory different to the GAP 4
home directory is that one  must  start  GAP  with  the  -l  switch,
e.g. if your private pkg directory is a subdirectory of mygap in your
home directory you might type:
gap -l ";myhomedir/mygap"
where myhomedir is the path to your home directory, which (since GAP 4.3) may be replaced by a tilde. The empty path before the semicolon is filled in by the default path of the GAP 4 home directory.)
To use the SymbCompCC Package you have to request it explicitly. This is done by calling
gap> LoadPackage("SymbCompCC");
true
The LoadPackage command is described  in  Section LoadPackage  in
the GAP Reference Manual.
If you want to load the SymbCompCC package by default, you  can  put  the
LoadPackage command  into  your  .gaprc  file  (see  Section The .gaprc file in the GAP Reference Manual).
SymbCompCC manual