I take it your daughter lives with you? Has she met the boyfriend yet? If not, that would be a good first step – don’t make it look like you’re doing as you please regardless of what she thinks. She is part of your life, and therefore will be part of his.
If she’s aware you’re in a new steady relationship (which she will be expecting at some point I’d have thought, especially at her age) then you can start asking her opinion with a view to seeding the ground. If she is totally unaware, I would slow right down. She has to be properly introduced and acclimatised first – don’t say there’s a date set. She has to feel a part of the change, which she ought to be anyway!
I too am moving in with my new partner after my ex left me 2 years ago. We’ve been together 18 months so in a similar situation to you! My 7 yr old is happy about this move as he gets on really well with my new man. My 20 yr old holds the same view although she is moving in to her own place soon, not moving in with us. My new partner has 2 kids & they will live with us on wkends. Everyone is happy about the situation as we have had lots of talks about it & meet up regularly (new partner lives 50 miles away so we are moving that way) it hasn’t been easy with the distance but like I said lots of meet ups & including them in decisions has helped a lot. Good luck with everything x