I have my source but I don't know how to make it a host file.
You only need the .dmb file and the .rsc to be able to run host files.
And you get those files by compiling the source, in Dream Maker.
Build -> Compile
Build -> Clean Compile (To keep out unused files)
Afterwards, your files ( *.dmb / *.rsc ) will be in the same folder as the .dme file.
In response to Leur (#2)
Doing the normal Compile before doing Clean Compile is an unnecessary step. You can just Clean Compile. And to get a zipped file with the necessary host files, you can go to Build -> Package Files... -> World Executable Files and select a save directory to save the zipped file, and hit Finish.