ok... so you want to animate the character when he walks?
there are many ways to do this, and i think you'd get the best response in the 'games' room since there are more people there usually

now, is this a side scroller or top view?

i had the notion that it was top view, in which case there is no sky, so tell me what you mean by your question

if you don't want the character to walk into other objects, then this would be the right place to get help, just be a little more specific