HELP! Challenge 1: Obstacles

I did the challenge, but there is problem I am having. When I checked on the select tile, there is no wall tile I created in the GameScene.sks for the Obstacles set. There is still just the grass and water tiles appearing in the new tile node named obstacles. When I added the wall tile in the Gamescene.sks to the background set , then there appears the wall tile, but that’s not how it should be as I check on the challenge folder source. The obstacles should just have the wall tile, but I don’t know how to set that up correctly. Any help or idea what’s wrong? Thanks.

I got it. I didn’t changed the Select Tile in the tile painter tool bar. I think you guys should add this step as well. I found out after skipping some pages and reading page 344.