How do I go about sharpening a 96" x 72" photo??

[hypermentality]

I have a friend of mine who had me come out and take a photo of his horse which he is wanting to have blown up on canvas to a whopping size of 96"W x 72"H!

I have taken the photo in RAW but it won't allow me to upload more than 14.65MB.. How do I go about properly sharpening it to where it looks the best? Could anyone give me a hand?

Here is the link to the file in my Google Drive..
https://drive.google.com/file/d/0Bxh6VBSk5ew3R3ZKbVN3eVpGeU0/view?usp=sharing

 

 I apologize about my amateurness.. A huge thanks to anyone's help in advance!

[Damien Symonds]

I'm so sorry.  I give a lot of advice freely here, but not where it coincides directly with my classes.

This is all covered in the Print Sharpening Class.

I hope you understand.