Well, I've never used NSE for anything but OverWorlds, but a sure-fire, straightforward way is by using a tool like TileMolester. If you load the palette of the tileset you wish to edit (in this case the sand-palette, I believe?) then scroll through the entire thing (doesn't take as long as you'd think) you'll eventually find where all the animations are. I believe the first one is the default flower, so if you see something that resembles that, you're there. And from there you can edit most/all of the animations for tiles, like the water tile, various flowers of the game, etc. So (more of) my advice is to just use TileMolester- but I'm kinda biased, so if someone can help you out with NSE it's probably easier.