The stock split won't take place until after the annual shareholder meeting in August.
According to the SEC filing, only stockholders owning shares at market close on June 6 will be able to participate in the vote. If you owned shares going into close that day, you should expect to receive a Notice of Internet Availability of Proxy Materials via email (or mail) through your broker. This will instruct you on how to cast your vote for the shareholder meeting -- usually you can vote ahead of the actual meeting day, so you don't need to be present at the 4:30 p.m. CT Aug. 4 meeting.
For this stock split, Tesla and its shareholders will have to take a few extra steps compared with last time, when the board simply announced its decision on Aug. 11, 2020, and swiftly split the stock on Aug. 31, 2020.