The order of Lord Caitanya:

amara ajnaya guru hana tara' ei desa
yare dekha tare kaha 'krsna'-upadesa
[Cc. Madhya 7.128]

"By following My order, you become guru." And if we strictly follow the acarya system and try our best to spread the instruction of Krsna… Yare dekha tare kaha 'krsna'-upadesa. There are two kinds of krsna-upadesa. Upadesa means instruction. Instruction given by Krsna, that is also krsna-upadesa, and instruction received about Krsna, that is also krsna-upadesa.

Krsna's upadesa is Bhagavad-gita. He's directly giving instruction. So one who is spreading krsna-upadesa, simply repeat what is said by Krsna, then you become acarya. Not difficult at all. Everything is stated there. We have to simply repeat like parrot. Not exactly parrot. Parrot does not understand the meaning; he simply vibrates. But you should understand the meaning also; otherwise how you can explain?

(From Srila Prabhupada's lecture on Sri Caitanya-caritamrta, Adi-lila 1.13 – April 6, 1975, Mayapur)