Open a terminal/shell and clone this repository into your home folder:
cd ~
git clone https://github.com/fgolemo/course-2018-networks.git
...then change into the qemu installation folder:
cd /net/ens/qemunet
Then continue with the first exercise: https://github.com/fgolemo/course-2018-networks/blob/master/1-setting-up-simple-local-net.md
...then follow the installation instructions over here: https://github.com/fgolemo/course-2018-networks/blob/master/INSTALL.md