Control of the undead in 5th edition is–like many things–quite simplified. The Create Undead spell is effectively synonymous with command undead spell. You would use create undead to animate remains and control them. Finger of Death is a spell available at higher level that kills living creatures and enslaves them permanently as zombies to your character.
Notions of contol undead, rebuke undead, command undead are lost at a glance, but Oathbraaker Paladins and some Socerer spells can command undead. The notion of rebuke undead on many forums is ridiculed as too subtle, by some–but there may be a point to that.
Overall–the notions of undead in 5e seem to have reviewed previous rules about creating undead from mostly remains of civilian corpses, whereas most necromancers are really on the lookout to find the remains of great warriors and turn them into death knights–by the score. This notion of creating armies of the undead appears to have some rules for necromancers, but all the remains need to be treated as unskilled plow hands no better than first level fighers.
Other techniques discussed are charming mid-level undead, namely a Shadow, and letting the Shadow loose in a warren of weak evil creatures–like goblins–and if the Shadow remains charmed, it will return to you with a thousand undead goblins! This is the most entertaining method of raising an undead army I read.