Install Mac Mail Signature

Dear All

In PC (Windows XP), if we have a simple HTM file and want to install it as a signature in outlook, we can do one of the followings:
1. Use Create signature by template
2. Copy the file directy to ..\Document and setting\(User Name)\Application Data\Microsoft\Signature folder
Then, it will appear and we can choose it from the list of signature.

I wonder if there is simillar way in Mac Mail, I mean how can we import a simple HTM file to make it signature.

Thanks alot.