Two things I can think of off hand:
Don’t ‘reveal’ yourself ‘dressed’. However, possibly have photos available in case you need to show what you look like,
Be prepared for the ‘usual’ questions: are you gay, do you want to transition, are you having sex with men, etc.
Also, possibly have something for your spouse to read that isn’t too frightening.
I actually cannot think of anyway to admit you’re cross-dressing other than simply beginning by saying you are a cross-dresser and taking it from there. Generally you will have some sense of the reception this information will receive. This should guide your approach.
Fot those contemplating a long-term relationship it is generally thought to be best to be up front before any commitments are made. For those of us who have been married for decades this news is a bit late but in the past 10-15-years the basic idea of honesty has been reinforced.