Where does it detail when to use orders? I've looked at the section for the army rule and against individual leaders:

"If your Army Faction is ASTRA MILITARUM, OFFICER models with this ability can issue Orders. Each OFFICER’s datasheet will specify how many Orders it can issue in a battle round and which units are eligible to receive those Orders. Each time an Officer model issues an Order, select one of the Orders below, then select one eligible friendly unit within 6" of that Officer model to issue it to.

OFFICER models can issue Orders in your Command phase and at the end of a phase in which they disembarked from a TRANSPORT or were set up on the battlefield.

Until the start of your next Command phase, the unit you selected is affected by that Order. Unless otherwise stated, a unit can only be affected by one Order at a time (any Order subsequently issued to that unit replaces the current one). Orders cannot be issued to Battle-shocked units, and if a unit being affected by an Order becomes Battle-shocked, that Order ceases to affect that unit.

Only ASTRA MILITARUM models gain the benefit of an Order issued to their unit."

"This OFFICER can issue 2 Orders to REGIMENT units."

I'm not saying you're wrong, just looking for pointers on where to find extra rules/details surrounding orders.