Can Some send me a tutorial or link that will teach me how to do it?
On one server, leave everything as is.
On another server, open blockland, click start server, click advanced config, and change the first option, Port, to 29000.
On the third, do the same as above, but change the port to 30000.
If you're using UPnP, that's it. If you're using port forwarding, follow one of many port forwarding tutorials on both of the two computers you changed server settings on, but using the port you changed it to (29000 or 30000) instead of the 28000 on the tutorial.