Before connecting, make sure you have installed a compatible client and the corresponding mods! See the tutorial here.

Method 1

Direct Connection

Advantage: much faster connection! Disadvantage: If the server IP changes (could happen at any time), you will need to find the IP again.

Determine Server IP Address

Visit the following link: mc.upsin.net/tut/ip.html

Alternatively, curl the page: curl.exe https://mc.upsin.net/ip; this will dump the IP in stdout. For linux, omit the .exe, like: curl https://mc.upsin.net/ip

Use the obtained IP address when you add the server to multiplayer in your minecraft client.

Method 2

Proxied Connection - Quite Laggy

This is the simplest version, but is typically quite laggy. Simply use the URL upsin.net as the server URL in minecraft. This URL will always proxy minecraft traffic to the server, but the act of proxying has some overhead causing lag.