Preliminary planning of the troops' kinds and numbers is an important tactical element that influences the battle result. In other words, you have a possibility to take decisions on what combat style fits you most: offensive, with prevailing creatures of high damage and long movement range, or defensive, with preference of a large number of shooters covered by stacks with high defense.
The recruiting can be done by following the link of the same name at the Character page. You will find a special menu with two troops’ scales. The upper one displays the amount of troops in your castle, the lower one - troops recruited by your character. After clicking any creature image, an animated enlarged image will appear on the right with the list of special abilities, and a full chart of the creature's properties below.
The numbers of troops in a stack is regulated in the blue column with two markers and a drag line. Single marker click will change the ratio at one unit, while dragging the thumb will lead to greater change.
Recruiting is extremely easy and comfortable. The main thing to remember here is that by recruiting a lot of troops of one kind, you limit other kinds' numbers. The maximum number of each recruitable creature type depends on your character's combat level and respective castle constructions, as well as faction skill level for knights and necromancers.