In this information, the term installation refers to one or more computing systems, the work the systems perform, and the people who manage, operate, and service the systems, apply the systems to problems, and use the output they produce.
The term installation exit refers to a routine which the system programmer adds or replaces in the operating system. It does not refer to the process of installing the operating system.
If you install an installation exit, you should use SMP/E. You can do that before or after the product is installed. After following these steps, do the APPLY or ACCEPT or both steps. For additional information see SMP/E for z/OS Reference.