When you want to grab a creature, you can use the Attack action. The target of your grapple must be no more than one size larger than you, and it must be within your reach.
Using at least one free hand, you try to seize the target by making a grapple check, a Strength (Brawn) check contested by the target's Strength (Brawn) or Dexterity (Acrobatics) check (the target chooses the ability to use). You succeed automatically if the target is Incapacitated. If you succeed, you subject the target to the Grappled condition. You can release the target whenever you like (no action required).
You can attempt to drag the grappled creature. When doing so, the creature's weight is doubled when calculating your Carrying Capacity and encumbrance, while moving the creature.
A grappled creature can use the combat action Escape to try to escape the grapple. To do so, it must succeed on a Strength (Brawn) or Dexterity (Acrobatics) check contested by your Strength (Brawn) check.