@fredlwal What do you mean?
When you create a definition, it just creates a reference point FOG will use to access the image.
Typically, people create the definition, assign the definition to a host, and then tell that host to perform a capture task. As the host is in the tasking, the image is being captured on the server. This step is unnecessary if you copied the image from another location.
The definition can be associated to any host though. It will use this definition during deploy tasks too.