Use a heel warmer, or make one using a diaper and warm water. Keep it on for several minutes. Bundle the baby, with the foot you will use out. Remember to stick the baby on either side of the heel, not on the bottom of the foot. We use microtainers, so be sure to have the right tube with you, using a scooper for the blood.
Two weeks seems a little old for a bili baby. Make sure it's feeding enough, with a good urine output.