In order to host a server that other players can connect to, you'll need to launch Wickland.exe with some additional options. There are numerous ways of doing this such as via batch file, shortcut, or cmd, but the easiest way if you intend to play on your server from the same computer is using Steam's launch options. Right click on the game in your library, then click properties, and you will be able to see the box.

Add the following to the options where MapName without the brackets equals one of the following:
(Note: "UDKWicklandGameDuelServer" is the other game mode but doesn't work correctly without the master server and instantly kicks joining clients out when it's set to this.)

Now when you start Wickland, the game will launch a dedicated server before launching the game and automatically connect you to it.

If you don't want to automatically connect to it, you can add "server" before the start of the launch options followed by a space, e.g. "server WLD-IxiJail?game=...". Using a batch file would be a better solution in this case.

The port can also be set to anything so long as you forward it to the IP address of your computer. 7777 is the default Unreal Engine port.

If you want to download a standalone dedicated server tool for hosting, refer to the first part of the developer's official guide - https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=343467301

You can join games in Wickland via a console command. Simply start the game up and press the tilde(~) key to bring up the console, and type in
e.g.

When you're hosting a server, in order for others to join it, you must port forward the port specified in the launch options to the IP address of your computer.

Refer to the following guide[portforward.com].