Complex sentence: At the start of the show, one of his friends would ring a bell at the bottom of the tree, therefore waking him up; he would then ride a slide that wound round the trunk of the tree to the bottom.
Split into simpler sentences: At the start of the show, one of his friends would ring a bell at the bottom of his tree, which would wake him up. He would then ride a slide that wound round the trunk of the tree to the bottom.