A little bit of searching can go a long way. Try searching for more general terms like "vocal mixing" over something unnecessarily specific like "how to make UTAU sound the right volume"
UTAU tends to level out the vocals anyway, provided you haven't edited the envelopes. Compression isn't really necessary, so as long as you manage to balance the levels right, you should be worrying more about how to make the vocal sound better with EQ, subtle reverb, and special effects for particular sections of songs.