Putting chicks under broody hen, when?

[GhettoRoo]

Hello. So my broody hen just sit her first night on fake eggs? What is the optimal time to sit, before putting live chicks under?
Can I do in it first week? Like in 4-5 day?

 

[Ameraucanas]

http://www.grit.com/animals/ten-secrets-to-a-successful-broody-hen-chick-adoption.aspx Hope this helps.