Installing QLC+ is pretty straight forward. Just head to the download page and get the version you prefer for the Operating System you're using.
QLC+ on Window comes as a self installing .exe package. Just double click on the file and follow the instructions that are displayed.
Chose whether to install QLC+ in its standard location (C:\QLC+) or another folder like C:\Program Files.
No admin privileges are required to install QLC+ unless you want to associate .qxw (Project files) and .qxf (Fixture definition files) to the related application. In that case, right click on the installer file and run it as administrator.
QLC+ on macOS comes as a DMG bundle.
Just double click on it and launch directly QLC+. Otherwise you can drag and drop it to the Application folder.
The official QLC+ package for Linux is delivered as Debian package (.deb).
To install it run the following from a terminal and the folder where you downloaded the package:
sudo dpkg -i qlcplus_x.y.x.deb