assignment in US patent

Dear all! I want to know when I can apply for ownership assignment in a US design patent application? what documents do i need?
urgent! anyone knows pls tell me! many many thanks!

assignment example

http://www.uspto.gov/web/forms/sb0015.pdf

http://www.legalzoom.com/legalforms/Patent%20Assignment.pdf

good luck.

assignment agreement and a power of attorney executed by the assignee