Brookfield Square's owner is seeking city financing help for an expansion project, while also delaying completion of that work by about a year beyond its original schedule. Mall operator CBL & Associates Properties Inc. would receive $6.55 million to pay for a new parking structure to be built west of Boston Store, and $450,000 to help pay for demolishing a small portion of the Sears store, said Dan Ertl, Brookfield community development director.