it depends on personal preference. i was first taught you anoint the candle by placing oil on your fingertips, then massage the oil from the middle up, then the middle down. later, i was taught you start from the bottom up, after that it was top down, and finally you place a drop on the top and a drop on the bottom. basically whatever works for you. i rarely anoint my candles with oil and the spells work fine.
if you have a candle in a jar, you could try anointing the jar, but i would either not anoint, or place it in some blessed water for a few seconds. i've never heard of an encased 7-day candle, but if it's inside an object, you can anoint the candle before placing it inside, or anoint the objects, just make sure if you have to move it you don't use too much and it slips.