Top left side of the F12 screen you should see speed controls. You can also set a conditional order "if speed < max, then set to max"
Keep in mind what is, to me, the most annoying "bug" in Aurora right now: If you make any changes to the composition of a task group (add a ship, remove a ship, transfer a ship, etc), the TG speed will reset to the max speed of the slowest ship in the Task Group. There might be a reason you don't want your ships to be moving at top speed (masking their top speed from another race, for example), so this is important to keep in mind when moving ships between TGs.