Hi BlackTiger,
Get the files you need from github at:
get wire folder and copy to Arduino/arduino-esp32
copy esp32 to Arduino/arduino-esp32/cores
To be safe, I would recommend renaming the old cores and old Wire folders just in case something blows up. Stickbreaker says this is a Beta version, so things may change and blow your stuff up.
Also, I am running into a bit of a problem in that I get a random failure every day or so. I think I may have a noise issue on the i2C bus, so I am going to clean up the board and keep monitoring this.
Here are some links to the background information that I found useful:
Good luck.
Don
background info
covers bus busy issues