The leaves
Now that you've gotten lots of practice crocheting the single crochet and half double crochet stitches, you're going to get a crash course in a lot of new stitches:
Grab your green yarn and let's make the first leaf:
Row 1: ch 7 (7)
Row 2: sl st in the second ch from the hook, hdc, dc, tr, dc, sl st, ch 7 (13)
Row 3: sl st in the second ch from the hook, hdc, dc, tr, dc, sl st (6)
Fasten off, leaving a long tail. Thread a needle with the tail; then use it to attach the leaves to the center top of the pumpkin. Weave in the end. When you've attached the leaves, it should look like this: