1.- Prepare linux enviroment
2.- Install Agent Installer 1.7 (IBM IM) 
3.- Install WebSphere Application Server 8.5.5 ND binaries
4.- Install IHS 8.5
5.- Start IHS 8.5
6.- Configure WAS ND 8.5.5
7.- Install Plugin
8.- Configure Plugin
9.- Configure SSL

1.- Prepare linux enviroment

# yum install compat-libstdc++-296.i686 compat-libstdc++-33.i686
# yum install compat-libstdc++-33.x86_64
# yum install gtk2.i686 libXtst.i686

NOTE: My last install was over RHEL 6.4 and I use the IM 1.7 64 bits, I did not need the enviroment prepartation because the IM runs great!!! but you will need to run the WebSphere Customization Toolbox (WPT) you will need to install 32 bits libraries.
Maybe you need to disble SELinux too by temporarily switch off enforcement, if that is your case just run this:

# echo 0 >/selinux/enforce

2.- Install Agent Installer 1.7 (IBM IM)

For this step you will need the file agent.installer.linux.gtk.x86_64_1.7.1000.20131119_2219.zip 

# unzip agent.installer.linux.gtk.x86_64_1.7.1000.20131119_2219.zip



all will be unzipped here, see next picture, then you only must run the installer

# ./install