Shove a creature

See Shoving a Creature

Roll Athletics vs Athletics or Acrobatics (they choose).

If you win, they are knocked prone or 5 foot away. You choose.

http://gdnd.wikidot.com/howtoplay:combat-basics

Note, there is a feat specifically for this which seems a bit underpowered (given it’s a feat and you’ve sacrificed an Ability score upgrade):

Charger

When you use your action to Dash, you can use your bonus action to take the Attack action with melee weapons, or to shove a creature.

If you move at least 10 feet in a straight line immediately before taking this bonus action, you either gain a +5 bonus to the damage roll (if you chose to make a melee attack; only applies to the first attack if you have the Extra Attack feature) or push the target up to 10 feet away from you (if you chose to shove and you succeeded).