Hola Gail, thanks for contacting us and sorry about our delay. The form "poneos" comes from the reflexive verb "ponerse" in the 2nd person plural ("vosotros"). The original form should be "ponedos" but we need to remove the -d due to phonetical reasons when using the 2nd person plural and pronouns starting by a vowel. I hope that this is clearer now. Gracias! Silvia.