In order to aim you must have some kind of aimable weapon
Such as: Shotguns, LMGs, Rocket launchers, etc.

Please equip your desired weapon and press RIGHT CLICK.
On a controller you have to use the top left button on your controller.

Here is how your mouse and controller looks like in order to aim.

On how to jump you simply have to press Space on your keyboard.
Or your A/X button on your controller.