Save your campaign level then exit to scenerio editor then test the blank map then load your campaign level then save your game in the editor then test the map then load the save then go to player then options then enable cheats.
You want those awesome premade levels? Now you can edit them!
Go into the favoured level, click save game in the menu. Goto scenerio editor and press test button. In the menu press load save game, click the desired level, then in the menu press ssave game. Go back to editor and load that file. It is now yours!
When you first start the game do you think "Hmm, lets see, I'll stockpile some resources so I can advance an epoch or two to stay ahead of my enemies."?
Well, I used to think that, but it is totally dumb. In Empire earth, the best defense is a good offense. I'm not saying divert all of your resouces to building up an army and then marching it out of your town and leave the town undefended. Build up a few walls and towers and research a few technologies, but create soldiers as soon as possible.
Chances are your opponent won't have soldiers, or many towers and walls at the beginning. If you run in and attack their citizens, it will deal a great economic blow right off the bat. This will make them unable to gather resources, and they will have to use all their resources to stop your attack. Also, if your enemy has control of an iron or gold mine, don't hesitate to send your troops in and take control of the mines.
The more mines you have, the more soldiers you have, and the best strategy is to outnumber the enemy, even if you have lesser technology. When you build up your defenses, steadily build up your army too, so when you are well defended you will have a formidable fighting force.
If you wanna weaken the enemy build a prophet, a canine scout, give the plague to the dog (using your profit) then send you dog in to the enemy camp and give the plague to as many enemies as possible before it dies.
P.S. make sure when you do this your dog isn't near any of your men or they will get it aswell