0 to put information in a form -- rellenar
to fill out an application form rellenar un formulario de solicitud
1 to add body weight so that you are not too thin -- engordar
He’s filled out in the last two years. Él ha engordado en los últimos dos años.
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
Podemos completarlo paso a paso, por muy largo que sea el camino, y no se puede completar, por corto que sea el camino, si ni siquiera marcas tu huella.