Map editor
Overview
Factorio includes a fully featured map editor. You can access it by selecting "Map editor" on the Factorio main menu, or by using the console command: "/editor" in game.
The editor allows the player full creative control and one can create a map with as much or as little resources as they wish. Movement uses the same controls as you have in game but no player appears, similar to the sandbox scenario.
Loading a Map From a Game
Scenarios can be created from pre-existing maps by using the --map2scenario runtime parameter along with the save to use when running the game from command line. For more info on runtime parameters, see Console#Command_line_parameters.
Saving your Scenario
Maps created with the map editor are saved as Scenarios via the in-game escape menu. These scenarios are saved to the User data directory. The scenario may then be played from selecting Play->Custom Scenario from the Main Menu. When saved and loaded, the game will load the map that was created by the map editor. If one wishes to add scripting to the scenario, they may do so by modifying the control.lua file created inside the scenario file.
Placing Entities
To place an entity (labs, powerlines, transport belts, mining drills, etc...), select "Entities" from your toolbox, select a tool, select what you want to place down, then click somewhere to place that item down.
You have three tools.
Cursor
Appropriate for most situations. Places one of the selected entity at the current cursors position. Much like the normal in-game mechanics.
Tip: Pressing "Q" on your keyboard will put the item you're holding away. Also see Keyboard bindings.
Spray
Good for resource piles and trees. You can select a size, intensity and speed, the larger the size, the more area that the spray places entities, the higher the intensity, the more often entities get placed, the higher the speed, the more rapidly the spray continues spraying while holding down the left mouse button.
Paintbrush
The paintbrush is virtually the same as the spray, only difference is that if you hold down the mouse button, the tool won't continue to place entities. Also good for resource piles and trees. Whether you use spray or paintbrush is personal preference, but for rapid controlled placement of resources and other items the Spray option is the best choice.
Deleting Entities
Cursor
When using the cursor tool, you can hover over the entity you wish to delete, and press "X" on your keyboard.
Spray/Paintbrush
When using either the spray or the paintbrush, right click to "unspray".
Placing Items
You can place items for the player to pick up in the editor. To do this, select the "Items" tab. From there, select what you wish to place down, then hover your mouse to where you wish to place the item down and right-click.
Removing Items
To delete items that you've placed, just like when placing entities, press "X" on your keyboard while hovering over the item you want to delete. The spray option is the fastest method for deleting items (you need to make sure you have intensity and speed at the maximum setting, and adjust size for the area you wish to clear). On the largest Size setting you can clear all items of one type fairly quickly using this method.
Placing Items Inside Chests (and other entities)
Press Q to deselect everything you currently hold in hand. After that left click on an entity to open its inventory. Now you can place items in that inventory. Based on your game settings you might need to use another event, see in the game-options.
Set up research
For information on setting up research in your scenario, see this forum post.