First off: What are Daimonin Arches? - They are the definitions of default objects, for example and ordinary orc, a door or standard food. These arches are vital for the editor and you can't work without them.
It is very important to know that there are two ways to load the Arches:
Load it from collected archive files. These should already be included in your editor and per default, these get loaded. Hence, if you don't want to care about arches, there's no need to worry about that.
You might ask yourself now: "Why should I spend my time downloading the arch package only to find out it takes three times longer to load?". Well, at some point during map making you will probably want to modify an arch, create new arches or new images. And for that task, you need to have the individual arch files in extracted form. However, don't worry too much about the loading time. You can collect the arches after modifying/adding what you want (see menu: "Resources->Collect CF Arches"). This will create new collected archives so you can both have your changes and load in short time.
Concerning maps: You don't necessarily need to have the Daimonin maps. You can just head off creating your own maps. Though, most likely you will notice that Daimonin map making isn't all that easy, and you'll want to have working examples to look at. Besides, you will want to link your maps into the existing Daimonin world and probably you'll want to test them too. For all of that you need the Daimonin map package.
Like the arches, you can get the maps either directly from CVS (see http://sourceforge.net/projects/daimonin/) or choose one of the download sites from http://daimonin.real-time.com/. Don't forget to set the default map path to your local map directory (menu "File->Options...").
Note that there is a special convenience option for browsing through maps: The "enter exit"-feature. You will probably know that in the Daimonin game, maps are linked to each other via so-called exits (doors, teleporters, buildings etc). You can select any such exit on a map (left click on it), then activate the menu "Map->Enter Exit" (or just hit <Strg> + <E>) and the map that this exit is pointing to gets loaded.