The credentials assessment may take about 3 month, not factoring yet the surge in volume the assessment body may received. It will definitely delay filing of your FSW application. To save time, you may want to visit Alliance of Credential Evaluation Services of Canada website (http://www.canalliance.org) to get information about the process and the documents required and get it ready as early as now.
Typically, you would be needing a certified true copy of your Diploma and Transcript of Records. Get these documents ready so that as soon as the official assessment body is identified, you can send your application for credentials assessment immediately. There could be other documents to be required. We will keep you posted.