Pre-sprint you want to be rolling along as fast as possible whilst seated, in a slightly hard gear, preferably in the slipstream of another rider.
Then ur gonna slam ur bike into the hardest gear, get out the saddle, and go ham. (This type of explosiveness primarily uses fast-twitch muscle fibres).
1000w is no joke so if you have done no previous strength training, don’t expect to hit those kind of numbers.
If you want to improve top end power, you need to work on lifting heavy weights or doing explosive exercises (jumping squats etc.) but make sure you know what you’re doing to reduce risk of injury.
Keep in mind though, that this will likely come at the cost of being able to do endurance training, which is typically more important than sprint power in road racing (until you are able to hang with the lead group anyway).