It is easy in itself. Like on Debian, just go into synaptic and install or use apg-get. Also if you can find a good how to to just follow.

The thing about QEMU is that it has a blithering number of options and reading the man page to get an idea is a major time sink. The other challenge is deciding how you run it and interface with it via the GUI, and file system. You can setup but there are various choices. Also it integrates with other useful commands too -- the commands to qcow manage images is a separate command. Or you can work with direct images and use dd, loopback, mount, etc to work with them. The nice thing is you get great Linux integration. The bad thing (or maybe good thing?) is helps to be good with man pages, bash scripting, command line, processes, networking, routing, and the Linux system.

So do not think of it like an OS setup though you will probably do an OS setup in a VM, but qemu just a complicated command. In the end you'll want to setup a folder tree, and some scripts to handle various things so it's baked in. I use it that way, for flexibility but VirtualBox is much easier since there are menus for or that.