I just did this 3 weeks ago, also purchased from a 3rd party dealer. Prior to the car being in your account, the app is essentially just the website mobile version. I'm assuming you've registered for an account, if not then from your desktop/mobile do so under the drop-down menu "Account", 2nd up from the bottom of the list, "Create Account". You don't need to be an owner to register. Once registered you see a box that says, "Purchased car from a 3rd party?" Once you click on this it will walk you through the process, you'll need to upload one of the required docs i.e. temp registration, purchase contract, etc. BUT now it's going to ask you to go to the vehicle, enter a code and change the name. And that's where I had to stop until I had the vehicle in my possession. Now, you may be able to finish this if you're on the phone with the dealer and they can do that step from their end. I just waited the few days for delivery. Once I had the car in my possession and did this process, had to start over as it doesn't save unless completed, it took 5 minutes max. In my case, the car was instantly in my account so the previous owner must have released it. If the previous owner has not released the car from their account, Tesla will contact them to do so, and that entire process is stated while you're doing this. Since your dealer is in contact with the previous owner, I would ask the dealer to contact the previous owner first and ask if or can they release it through the app. It's just a couple-click process, and most owners do it immediately because you maintain c.c. payment methods in your account and any Supercharging, upgrades, etc would be billed to their credit card. If that's done it will show up in your account quickly, in my case instantly. If Tesla gets involved in having to contact the previous owner to release, I can imagine that would bog it down. Once the car is in, when you log on to the App it will be a completely different experience.