Using the Attack action, you can make a special melee attack to shove a creature, either to knock it proneor push it away from you. If you're able to make multiple attacks with the Attack action, this attack replaces one of them.
The target must be no more than one size larger than you and must be within your reach. Instead of making an attack roll, you make a Strength (Athletics) check contested by the target's Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use). You succeed automatically if the target is incapacitated. If you succeed, you either knock the target prone or push it 5 feet away from you. If you succeed by 5 or more, you can instead push the target 5 feet away AND knock the target prone or push the target 10 feet away from you.
With this option, a creature uses the Shove action to force a target to the side, rather than away. The attacker has disadvantage on its Strength (Athletics) check when it does so. If that check is successful, the attacker can instead move the target 5 feet to a different space within its reach. If the attacker succeeds by 5 or more, the attacker can move the target 10 feet to a different space within its reach.