1)  Setup

vi .cshrc

<ADD>

setenv IDLUTILS_DIR ~/idl/djs        # You might use idlutils instead of djs 
setenv IDLSPEC2D_DIR ~/idl/idlspec2d 
setenv XIDL_DIR ~/idl/xidl  
setenv IDL_PATH +$IDL_DIR\/lib:+$IDL_DIR\/examples:+~/idl:+pro/
  <The last line require IDL_DIR is set properly.  This is your job!>

2) IDLUTILS (a.k.a. djs)

Grab and unpack the tar file or CVS distribution from the SDSS website:
http://spectro.Princeton.EDU/idlspec2d_install.html

cd idlutils
bin/evilmake clean
bin/evilmake 


3) IDLSPEC2D

Grab and upack the tar file or CVS distribution from the SDSS website:
http://spectro.Princeton.EDU/idlspec2d_install.html

cd idlspec2d
$IDLUTILS_DIR/bin/evilmake clean
$IDLUTILS_DIR/bin/evilmake 


4) XIDL

Grab and unpack the tar file from my website:
http://www.ucolick.org/~xavier/IDL/index.html

cd xidl
bin/evilmake clean
bin/evilmake 

5) Run IDL and try  

  IDL> .com x_splot

and 

  IDL> a = djs_median(findgen(100,100),1)