Neither of these are anything like American yams.
There are many ways to cook it, and you can eat it raw. Here I have cooked it with chicken, using the fat from the chicken to crisp up the potatoes like Japanese style fries :)
Chinese Yam Fries
1. Put boneless chicken pieces in a pan, skin side down.
2. Scrub a piece of yam, slice into 1.5cm slices.
3. When the chicken fat is starting to coat the pan, add the yam.
4. Cook yam until golden on both sides.
5. Turn the chicken.
Chicken and Tomato Stew
1. Cook chicken as above.
2. While it is cooking, chop vegetables you want to use. In this case, 2 small eggplants, one young green onion, piece of negi leek.
3. Add veggies to pan. Toss in the chicken oil.
4. Add a glass lid and cook for a few minutes.
5. Cover with a can of chopped tomatoes.
6. Simmer for 5 minutes.