Atlase issues

Who tells me how to work with atlases now?
My preloaders not working now. .

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I'll say this once again, but nothing should have changed about atlases between 3.2 and 3.3. If you find that there's a  difference, please specify exactly what it is.

If you're not upgrading from 3.2, but from 3.1 (which did have a completely different atlas system), then you can follow the steps here to get atlases working like they used to before 3.2:
http://community.stencyl.com/index.php/topic,35479.0.html