Resizing in Elements 5

I am trying to get a photo resized to 768 by 511 (approx) with a file size not to exceed
400K. How do I do this? Every time I change the pixels, something else changes. I don't think I am supposed to change the resolution. I think that is supposed to stay at 72. In Elements 3, this was done by changing quality down to a 7 or 8. How do you lower the quality (and resulting file size) in Elements 5? I did a search in Photography review, but nothing turned up. (Yes, I also looked in the manual - I don't see an answer) Suggestions?