In Actionscript 2.0 you use;
Add to your last frame, the end of your timeline...
Remove framenumberhere and insert the number where you would like the loop to begin e.g 1.
I hope this helps!
Is the code any different for AS3?
I don't think so, although I am not to familiar with AS3.
Give a go and see what happens, you will get a syntax error if it is incorrect.