The Bishop of Rome (the word "Pope" was invented much later) could not appoint Bishops in the territory in which the Bishop of Alexandria had jurisdiction.
There was no such thing as primacy of the "Pope" at the time.
Let the ancient customs in Egypt, Libya and Pentapolis prevail, that the Bishop of Alexandria have jurisdiction in all these, since the like is customary for the Bishop of Rome also. Likewise in Antioch and the other provinces, let the Churches retain their privileges.
You can read all about it here:
The Sixth Nicene Canon and the Papacy
"Let me, at the risk of being tedious, state, first of all, my understanding of the passage. The supremacy of the Bishop of Alexandria had been contested by the Meletian bishops. They had, asked him, if not in words at least in facts, upon what warrant he based his claim to rule over and depose his fellow-bishops. If he had a title let him produce it. Now the Alexandrian prelate had no written document of any kind to produce. The Council of Nicaea, therefore, came to his assistance, by decreeing that the Patriarch's [16] authority must be respected, and that for two reasons: first, because it was (archaia), immemorial, aboriginal; and second, because it was sanctioned by constant recognition on the part of the Roman Pontiff. Two very good reasons".......A quote from the above.