The few steps of installations:
1.
Choose the path to the IUA functions or set your own path.
As the ordinary CATIA user you will add or modify the following lines in your
USRENV.dcls file. (e.g. the path for the IUA functions will be $HOME/.iua).
  catia.iuaproc_usr = '$HOME/.iua';
  catia.iuamodule_usr = '$HOME/.iua';
  catia.iuapanel_usr = '/$HOME/.iua';    
As the CATIA administrator you will add or modify the following lines in ~/dec/CATIA.dcls file.
  catia.iuaproc = 'the directory containing the standard IUA procedure source files';
  catia.iuapanel = 'the directory containing the standard IUA panel source files';
  catia.iuamodule = 'the directory containing the standard IUA load module files';
                or
  catia.iuaproc_usr = 'the directory containing the customer's IUA procedure source files';
  catia.iuapanel_usr = 'the directory containing the customer's IUA panel source files';
  catia.iuamodule_usr = 'the directory containing the customer's IUA load module files'; 
2.
Set the paths in the interactive CATIA function IUA.
3.
Copy desired IUA functions to defined directories.
  cp *.iuaproc "catia.iuaproc"  or cp *.iuaproc "catia.iuaproc_usr"
  cp *.iuapanel "catia.iuapanel"  or cp *.iuaproc "catia.iuapanel_usr" 
4.
To start the EMAGRID function for example, key /m emagrid.
5.
Add the new menu for the installed functions.
A the ordinary CATIA user you will add the following line to your USRENV.dcls file
   include( 'ema.dcls' ) ;  
to load the menu from the ema.dcls file in your home directory for example.
As the CATIA administrator you will modify the ~/dec/CAFRM.dcls file.
6.
To put a colors on the CATIA buttons.
As the ordinary CATIA user you will create or update the .Xdefaults file in your home directory.
As the CATIA administrator you will modify the ~/adm/xcfg/Catia file.

Example of the EMA.dcls file.
Example of the USRENV.dcls file.
Example of the .Xdefaults file.

The path to the current USRENV.dcls ... echo $CATMSTR
The path to the current IUAs ... catpath -l -A catia.iuaproc
                                 catpath -l -A catia.iuapanel
                                 catpath -l -A catia.iuaload
                                 catpath -l -A catia.iuaproc_usr
                                 catpath -l -A catia.iuapanel_usr
                                 catpath -l -A catia.iuaload_usr

Whew!....you really didn't read  all of those...did you?