Why do you want to call this directly?
It's actually something used internally by DevForce when looking for and initializing Code First models. The method will search for any *.ibmmx files embedded in the given assembly and merge the contained metadata into the EntityMetadataStore. This all happens automatically, or is supposed to, whenever a new entity type is seen in a query or save list. The assembly normally passed into the method is one holding entity declarations, so should already be probed.
If you're seeing a problem with your Code First entities, please let us know the details of the problem.