Create a button. Assign a script to stop the main timeline or to goto the last frame of it (I don't know what exactly you want).
on (release) {
_root.stop();
}
You have to select the button by clicking it on the stage. U will see the title in the actionscript panel changing from "frame actions" to "object actions". U don't have to place the "on" action. Just place the "goto" and the "on" will be placed automatically.