Installer. A software utility that installs an application.

“After inserting the disk, you need to run the install.”

An installation. (Usage originated as a truncated form of the word installation.)

To connect, set up or prepare something for use.

“I haven't installed the new operating system yet because of all the bugs.”

To admit formally into an office, rank or position.

“He was installed as Chancellor of the University.”

To establish or settle in.

“I installed myself in my usual chair by the fire.”