IPA: /ɪnˈstɔːlər/
KK: /ɪnˈstɔlər/
A person or program that sets up software or equipment so that it can be used.
The installer guided me through the setup process of the new software.
Installer → It is formed from "install" (from Old French *installer*, meaning to place in position) and "-er" (meaning a person who). An installer is a person who places or sets something in position.
Think of someone who 'places' ('install') something in position — that's what an installer does.