First I had to configure mikrotik router to act like DHCP server for Rasbperry PIs and to map different ports to connected Raspberry PI's port 22 (SSH). So I can access them through SSH and they are behind the router.
Burning Hypriot OS image to 4 SD cards
and afterwards assign each on proper hostname (master, node1 .. 3). The later is a bit different if you do it on Windows (you have to modify the configuration on each SD card instead of passing parameters to flashing tool).
Kubernetes installation
Pretty much as blog post. However, the first time I did it it wouldn't install. Installation was stuck at waiting for kubeadm init.
The best way to figure out is to look at Docker logs for problematic containers (you'll see them marked as restarted or failed) and inspecting kubeadm logs.