Step 1: Download the latest release or pre-release (available as zip or tar), and save it in a temporary location on your computer.
Step 2: If you are going to install IRIS in a folder where an older version already resides, wipe all of the old files out first.
Step 3: Unzip the archive file into a folder of your choice on your hard drive, such as C:\IRIS_Tbx or ~\IRIS_Tbx. This folder is called the IRIS root.
When installing a new version of IRIS, we recommend that you also remove all of your older versions from the Matlab search path, and preferably restart Matlab.