Had down lighters in the bedroom. Replacing it with tube light fixture. Each down lighter had two black and two red wires attached to it. New fixture has a connector with blue and brown wires from the unit. What do I conect to N and what to L?

Are you outside North America? Sounds like it from the wiring colors. Usually red matches with brown (these are L) and black matches with blue (these are N).

In case you were wondering, red and black were the old wiring colors; they were changed to blue and brown to help those who are colorblind tell them apart.