How do you place locks+keys, powerups, and go back in forth in tilesets?

I'm going to start on my first level today, and it requires keys, locks, and powerups.
Its going to be mostly enviormental and stuff, but because the levels I've made with level editor usaly are messed up because I cant layer correctly, I need help.

Please [search], read the [faq], and read the manual before posting any questions.

Here is a better answer.
All you need to know is to use the layers. It's very easy. Layer 0,1 and 2 is backround layers.
Layer 3 is the ground layer, it makes things solid. And layer 4, 5, 6 and 7 is object layers.

To learn how to use this, you shouldn't care about layer 0, 1 and 2 at all for now.
To answer your question 1. To place any object, including keys, locks and powerups you must have layer 4, 5, 6 or 7. If you have layer 0, 1, 2 or 3 you will not be able to place an object. To go back and forth between objects and tiles you change between the layers. So just remember that layer 3 is for the ground and layer 4, 5, 6 and 7 is for objects.

And to change tileset, you can click the tileset number. If you can see above the tileset, it says tileset A and B, click there and you can switch tilesets. Or simply use your scroll-wheel in the tileset window.

Hope this post helps.

Here's a quick-and-dirty description of each of the layers:

• Layers 0-2 can only hold tiles, are only for visuals, and always appears behind Juni.
• Layer 3 can only hold tiles, and any tile placed on Layer 3 will become solid.
• Layers 4-5 can only hold objects, and always appears behind Juni.
• Layers 6-7 can only hold objects, and always appears in front of Juni.

EDIT: Fixed a typo.

Actually, layers 4-5 put objects behind Juni, layers 6-7 put them in front of her.

Oops, sorry. That was a typo, my bad.