Daybreak Games announced the 10th-anniversary celebration nad its scope in DC Universe Online which makes it the biggest one in the game's history.
Starting off with smaller things, DCUO now features new missions in the updated Metropolis Anti-Matter Invasion Zone. These include daily, weekly and bounty missions that were created especially for the anniversary.
To get into them, just open the Mission Journal and look for Monitoring the Situation. Alternatively, you can use the Warp Menu to go directly to the Metropolis Anti-Matter Invasion Zone.
If you are looking for something more hardcore, the devs got you covered here as well. Anti-Monitor is up to no good once again and is attempting to use a paradox that is said to be the most powerful and destructive one in the Multiverse. When there is a paradox involved, you know Flash and Zoom can't resist attending the party but it remains to be seen if this one will be too much for them.
Similarly to the new missions, you can access the new Speed Force Flux raid through the On Duty menu. Speed Force Flux Elite version is the end-game difficulty raid so make sure you are geared properly before queuing up.
Queue up for Centennial Collapse in the On Duty Menu if you are looking to get into some of the goodies from the previous anniversaries. Keep in mind that the actual anniversary is on January 11, 2021, so make sure you visit the game then as well as the devs hinted there could be some gifts up for grabs.