It takes a little while. People need to adjust. For me it didn't seem to take long before people basically "forgot" that my name didn't used to be Jason. They forget that I wasn't "he/him/his" before. Some friends have come across old pictures from high school or whatever and they'll be blown away because it's like I'm a completely different human being from the one they knew before. Once you come to a name and start really living as the person you're shooting to be, things fall in line easier. Once you see yourself as (insert name here) and you take on that role, people start to view you as that role over time. Everyone's going to have memories and I've battled that thought on numerous occasions where I've just wanted to brainwash people into never having known who I was before but that's a whole different issue. Point being, you're in the awkward in-between stage and once that stage has gone away and you're living as the "you" that you want to be, everyone else is going to see you as that person as you grow more and more in that skin.
Also a side note, now's a good time to start really putting together who you want to be. If there are things that not being born bio-male has caused you to hold back doing, or somehow has caused dysphoria that ultimately caused other problems, change it while you go into your new skin. For instance with me, I had HORRIBLE anxiety issues and I would get anxious during certain things (example: long car rides). Once I started transitioning, I made an effort for the "new me" to not be afraid of riding in a car for 4 hours. Hell, I moved 4 hours away and made the commute all the time. So that way it was one less thing for me to feel was "broken" about me when I was at a stable point of being transgender. Things like that may not apply to you, you may be exactly who you want to be personality-wise, but I figured I'd offer the advice.