I pretty much followed this guide:
With a self-built copy of Ryan’s firmware I could not get the esp01 to talk to the SKR over the port made for it on the SKR. I could get it to talk to the SKR board if I put the esp01 on the serial port of the TFT35, I.e. in a daisy-chain. I presume I’d have to change some of the serial port configurations in Marlin to actually get it to work on the esp01 port on the SKR.
Once I flashed the firmware on the esp01 I don’t recall having issues connecting to it’s own wifi network to then get it on my own network. No USB to do that, you connect to it’s wifi SSID temporarily.