Lucky for you Dedis are like Default Add Ons for blockland, like Mission Editer, but minus the confusing things to type.
Step 1: Open up your Blockland Folder (Right click Icon, click properties, then click Find Target)
Step 2: Where you see Dedicated right click it and click Edit
Step3: Where it says "bedroom" highlight and replace with the map name of the one you want it to host, It wont always work though
Step 4: Save the edit and double click the Dedicated Icon, a Command Prompt screen should open up.
Step 5: It should say something in a box their like Your Dedicated server hasn't been registered with RTB
Step 6: Ignore it and join the server, it will fix the error in the Command Prompt
Step 7: Nothing, it should work, but it might take a while to start up fully.
To shut it off, click the X to close the Command Prompt for the dedicated server. Enjoy