Okay so I have 2 tiles one that's a wall and one that's a walk...
Drop them in the /tile/ folder.
Now comes the hard part, well not really. Open up tileInfo.xml, you should see a list of tiles.
There are basically 3 types of tiles.
less then 0 (<0)
Walls (can not be walked on)
an empty image (this is also the default image if something breaks down.)
greater then 0 (>0)
paths (can be walked on)
Its that simple if there negative there walls if there positive they are paths.
Now lets add our two test examples.
loc is just the file name in the tile folder. You can add your own folders but they have to be in the tile folder.
info (does nothing) description of the title.
wall (does nothing for now) true or false if its a wall.
id specific number that differentiates it from all the others. If your putting in your own tile set probably best to just assign it its own starting number (ie 100 and -100).
And that's it.