Find the level plain you wish to attack, when you click it you can either scout it or attack it. Scouting is worthless, since we know how many troops are there. Make sure someone doesn't own that plain first (it would put their name on it). Then look at the chart below, and see how many troops are DEFENDING that level plain. Send more troops then the wild has. Click attack and tell it how many of each soldier to send and select a Knight (one without a role), and select "March".
Click for unit numbers in wilds--->