I think you misread the learn to play booklet….also if you have not yet built your models, of course you haven't played the introductory game.
Issuing orders, basically means you put face up order tokens next to certain units (howmany and which kind of units depend on the command card you choosed at the beginning of round)
Activation - you and your opponent alternate to avtivate units 1 at a time, starting from the player with priority. Activating a unit means that unit can take two actions out of the list mentioned on page 10<of the lear to play booklet. how to actually perform those action is explained later in the same booklet. When it is your turn to activate a unit, you can either choose to activate one of the unit to which you issued orders, or to randomly select an order token from the order pool (which is made by all the order token you didn't use in the command phase). If you go for random selection you must activate a unit of the kind depicted on the order token you took out.
So, e.g. in the introductory game, you have 2 corps unit - the triangle - a support unit - sort of 8 shaped figure - and a commander - the winged figure. If during command phase you choosed the 2 pip card, you had given face up order token to 2 units, let's say you choosed the commander and the support unit. When it is your turn to activate a unit, you have three possible choices:
- activate the commander
-activate the support unit
-choose randomly between the two remaining tokens (which are both corps units in this example). If you do so no matter which token you take out, you may choose which of the two corp units you want to activate.
So issuing orders to a unit just means you can choose at which point of the activation phase you will be able to activate it (instead of waiting untill you randomly selct the proper token from the order pool)
This is really important, since activations are alternated between the two players, so activating a certain unit at a certain time (not too early or not too late) is very important. For example, your unit maybe too far from the enemy to be able to shoot them, so you move it. Still too far. You move it again. Now it is your opponent's turn. He now has one of his unit in range to shoot to the unit you just moved. So it can spend its first action taking AIM, and the second action to shoot.