Flexheader3 Module Installation is very easy, because it uses the Joomla! Extension Installer.
- Download the module installation file from this site to a local directory or just use "Install from Web" in Joomla 3.x
- Login as an administrator into your Joomla! Backend
- in the topmenu navigate to Extensions -> Install/Uninstall
- In the extension manager use "Upload Package File" -> "Browse" and then the "Upload File & Install" button
- Got to the module manager and click on "Flexheader3"
- enable the module
- choose a module position
- check the "Module Assignment" Tab in Module Settings an enable Flexheader for all of your menu entries
- save the module options
- a help window will appear on the frontpage that shows you the filename for use with flexheader3
- name your picture as shown in the help window