When I first started going out, my daughter had moved into her own apartment, and my wife was spending weeks at a time out of town.
That gave me plenty of opportunities to be out and about and dress at home. I might cover my top and wait until I was out of the neighborhood before I put on my wig, but other than that, I was fully dressed.
When my wife stopped going out of town, I had to go to Plan B. I had searched out parking lots and garages as businesses that were mostly empty, and would park there to change. A lot of time, we would meet at a hotel, and I would find a bathroom to change in. I preferred family restrooms, but would often go into the men's or women's restroom and change in one of the stalls.
Eventually, I met a CD friend whose wife was supportive. I could change in one of her extra bedrooms. She and her wife moved out of town a year and a half ago.
After that, I would make arrangements with my wife for her to go out for a couple of hours while I changed. Now, I've made some good GG friends at a local consignment store. I buy a lot of clothes there and they let me try on clothes there just like any GG, even if I'm shopping in male mode. They will also let me use one of the changing rooms, or the back storeroom to change before events.
I'm posting this as a public service to help girls in a DDT marriage to find alternate places to change, if they can't change at home.