Many templates include a character you can control using your keyboard, mouse, or controller. In Unreal Engine terms, this is called a Pawn.
You can view existing controls for your Pawn and configure new ones in the Input section of the Project Settings. To open it:
From the main menu, go to Edit > Project Settings.
In the left sidebar, scroll down to the Engine section, then click Input.
Expand the Bindings section to edit the:
Action Mappings: Defines the keys that control actions such as jumping.
Axis Mappings: Controls movement. Depending on the template, movement may be restricted on one or more axes. For example, in the Side Scroller template, the Pawn can only move left / right and jump.