Hi @pieper. With your answer and some tries I finally achieve my goal. I will add to the post my code solution:
# Import modules
from __main__ import qt, slicer
# Create the message
message= "¡Hola desde Slicer 3D!"
label= qt.QLabel(message)
# Change the Font and Size:
etiqueta.setFont(qt.QFont('Times', 15))
# Use the Object statusBar()
barra_estado = slicer.util.mainWindow().statusBar()
# Add to the StatusBar the Label
status.addWidget(label)
# Reformat the StatusBar
status.reformat()