The video tutorial on using SDX, including the instructions of how to setup the xml files for sdx to use is forthcoming. The delay is because we are striving to make sure everything is perfectly clear for the absolute beginner. Several of us have gone through the written tutorial line by line a few times, improving it on every iteration. I understand that folks are eager to move forward with modeling, but unless we get this right the first time, we will be buried in support questions.
Remember, as it relates to adding new game objects to 7d2d, you only have to run sdx one time without any mods selected. Once that's done, you can drop most unity3d files (any that do not have required scripts for animation, lighting etc) into the Mods/SDX/Resources folder found in your game directory, then manually add the new object as a new block into your blocks.xml. No need to re-run sdx for that. The standard format for the lines you need to add to the basic block are:
<block id="2013" name="newblock"> <!-- Need a unused ID number and name -->
<property name="Shape" value="ModelEntity" /> <!-- required exactly as typed -->
<property name="Model" value="#NewBlock?NewBlockPrefab" /> <!-- required - #____ is the name of the unity3d file, ?__ is the name of the object inside that file -->
<property name="Material" value="wood" /> <!-- pick any material, but one with some stability, like wood, metal etc. -->
</block>
Look at a similar block in the blocks.xml for other properties you might want to add, like to enable picking up the block, enabling collision with the block, etc. Add those lines as you desire.
The launch of the website is scheduled for early September, but there is a chance that it will be available sooner than that. Patience please, we are nearing the goal.