Before installing Munin on server01 apache2 will need to be installed. The default configuration is fine for running a munin server. For more information see HTTPD - Apache2 Web Server.
First, on server01 install munin. In a terminal enter:
sudo apt install munin
Now on server02 install the munin-node package:
sudo apt install munin-node
On server01 edit the /etc/munin/munin.conf adding the IP address for server02:
## First our "normal" host. [server02] address 172.18.100.101
Replace server02 and 172.18.100.101 with the actual hostname and IP address for your server.
Next, configure munin-node on server02. Edit /etc/munin/munin-node.conf to allow access by server01:
Replace ^172\.18\.100\.100$ with IP address for your munin server.
Now restart munin-node on server02 for the changes to take effect:
sudo systemctl restart munin-node.service
Finally, in a browser go to http://server01/munin, and you should see links to nice graphs displaying information from the standard munin-plugins for disk, network, processes, and system.
Since this is a new install it may take some time for the graphs to display anything useful.
The munin-plugins-extra package contains performance checks additional services such as DNS, DHCP, Samba, etc. To install the package, from a terminal enter:
sudo apt install munin-plugins-extra
Be sure to install the package on both the server and node machines.