I am buying a new home from a home builder and have signed the agreement and given a significant amount with agrement. The house will be delivered in a few months and will be settled at that point of time. Can I apply for the new home credit with my tax file before April 15. If yes, how do I go about it. If not, do I have to wait till next year to file for tax credit or can I do it mid year with some amendment.
I would really appreciate if someone could clarify this and help me out.

No. You will get credit only after it is settled.
Then you can file amended tax return.
This credit is available for first time home Your U.S. Tax Return: First-Time Homebuyer Credit (http://taxipay.blogspot.com/2009/01/first-time-homebuyer-credit.html)