ok some quick logics things before I go into the history. Napoleon starts out garrisoned in your only stockade at the end of the town of Eylau. The Russians immediately attack you, so be prepared to move your troops right when it starts. You cant build and you have no reinforcements, you do however have reserves you can move up from the back of the map.
This scenario starts right after General's Augereau's unsuccessful charge. The Russian army has moved into the edge of the town with three divisions, you only have one division defending it. Move up your reserves to prevent the capture of Eylau. You also have Davout's force who has hit the Prussian and Russian left flank. Remember to save your forces, because there are still Russian and Prussian reserves you must completely destroy after you stop the attack at Eylau. This was the last main battle that the remnants of the Prussian army fought in. Though you are outnumbered, your army is more superior because most of the last reserve units are Napoleon's direct guards. Historically, the French blocked the Russian offensive, but lacked the forces and morale to pursue. See if you can change history and crush the Russian(and Prussian) Army!