In order to join StrongCraft.org server you need Minecraft client (Java edition). All major versions from 1.8 and up to 1.16 are currently supported, but for best user experience you should use Minecraft 1.8.9.
Once you have your Minecraft client up and running, simply join:
Also be sure to check out the rules.
We're looking forward to seeing you online!
PS: Your website account has to be registered ingame (once you join the server).