This video will teach you how to control the camera and give your units orders on the battle map.
In battle you can select a single unit by left-clicking on it, or select multiple units by left-clicking and dragging a box around them. You can also hold down Ctrl when left-clicking to select multiple units individually. Units may also be selected by left-clicking their unit cards, seen on the bottom of the screen here.
To move the camera around the battle, use the WASD keys; you can hold down shift to move around a little faster. Use the Q and E keys to rotate and scroll the mousewheel to move up and down. Lastly, hold down the mousewheel and move the mouse to rotate the camera in any desired direction.
You can press ESC at any time to open the menu, which allows you to change the options or even concede the battle.
To order units into position, simply right-click where you want them to go. If you right-click and drag on the terrain, you can order selected units into more precise positions. Hold down spacebar when in battle to see unit destinations when they are moving.
Press Ctrl + A to select your entire army at once, and left-click away from your army to deselect any selected units. With multiple units selected, hold down both ALT and drag your cursor to order them to move together, whilst keeping their formation. You can press BACKSPACE to halt selected units at any time.