To start a mod, click the Create New Mod button in the game start menu. This copy of your mod resides on your computer in the directory you specify.
To start the level editor, start your newly created mod, then click the Editor button in the game menu. The level editor is a very powerful tool, and even includes a visual scripting language. When you start the editor, you start with a new blank map. You can test play your map by clicking the play button on the editor toolbar. When you're done testing, just press ESC to return to the editor.
To add an opponent, click the New Bot -button. Then set it's side to Evildoers, and you can test how it attacks you. Similarly you can create for example movable object, walls, items and lights by using the buttons above.
When you've created a new bot, item or object, you can edit many of its parameters by clicking on the said item/bot/object once, and choosing the item-specific parameters you wish from the left hand side of the editor screen. Notice the different sheets for scripts/physics/animations, etc, which you can open from top left.
All of the resources in the main game are at your disposal, the graphics, the sound files, and all of the items, creature types and others. The game always looks for a named resource, such as a texture file, first from the mod directory, and if it's not found there, it looks in the main game directory. That way you can replace any of the main game resources with your own resources.
Always remember to save your map. CTRL-S works. Every time you save a map in the editor, the game will create a backup. You can find them in the "My Documents\Driftmoon\map_backup" folder. So if you mess up your map, you can always go back.
You can copy and paste objects using CTRL-C and CTRL-V. You can also copy a group of objects (by dragging a selection box around the objects). When copying a group, the game will even auto correct scripts and joints that reference objects within the group. So if you have two objects that are joined together by a joint, copying them together will ensure that the copied result also has the joint. You can also use the copy-paste feature between maps, and it is the easiest way to copy objects between different maps - just copy from one map, load up another map, and paste.
It is also possible to export and import single objects or groups, and it behaves exactly like copying and pasting objects.
When you've finished a version of your mod, you can upload it to the Driftmoon mods list for others to download. You can also update your mod the same way!
If you need screenshots of your mod for marketing purposes, you can use the ingame screenshot function. Just press Scroll Lock, and for each key press, the game saves two screenshots into "My Documents/Driftmoon". The other one is what you see in the game, and the other one is without the GUI (=user interface). Note that you can take a whole bunch of screenshots during one play session, and all of them will be saved - there's no need to capture the screens only one at a time.
The best way to learn modding is to see how other mods have been created. So start any mod, open up the editor, and have a look.