The actual lighting of the lamps (compare the marginal references) was to be done to set forth symbolically the special presence which God had now Numbers 7:89 actually established among His people.
Related Commentaries of Numbers 8:1
Numbers 8:1-4
1 And the LORD spake unto Moses, saying,
2 Speak unto Aaron, and say unto him, When thou lightest the lamps, the seven lamps shall give light over against the candlestick.
3 And Aaron did so; he lighted the lamps thereof over against the candlestick, as the LORD commanded Moses.
4 And this work of the candlestick was of beaten gold, unto the shaft thereof, unto the flowers thereof, was beaten work: according unto the pattern which the LORD had shewed Moses, so he made the candlestick.