In order to access the Online Time Trials, you’ll need to unlock Sport Mode, by completing Menu Book 9 (“Championship: Tokyo Highway Parade”) in the GT Cafe single player hub. As it’s just you against the clock and not a direct, head-to-head multiplayer event, PlayStation Plus is not required.
You’ll usually need to be within 3% of the fastest time globally once the event finishes in order to secure “gold” status and a 2m credit bonus prize. There’s smaller prizes of one million for being within 5%, and 250,000cr for bronze at 10% off.
The events update every Thursday, with each individual challenge usually remaining available for two weeks and the oldest of the two events being replaced each week. You can look forward to the next new Time Trial arriving at 0700 UTC on Thursday April 10.