Most popular search tools:
Statistics Canada - known as "StatsCan", the best place to start for social, economic, and demographic data about Canada, the provinces and territories, and cities.
Attached is a slide deck from a presentation by StatsCan staff about how to use the 2016 Immigration, Ethnocultural and Housing data releases. It makes for a good tour generally of the structure of the StatsCan census data reports and website.
Other ways of searching and using Statistics Canada data sets (rather than just the summaries provided by the main website) are the following:
Government search engine (Google custom search) - use the search box at the top of this page to find all kinds of government reports, many of which include statistics. It can also be used to search websites of other governements and intergovernmental agencies (like the United Nations), not just Canada.
Statista - a commercial database of statistical summaries on all kinds of topics; not Canada-specific, but some Canadian data
PEI-specific - aside from StatsCan and searching the PEI provincial government websites using the Government search engine, also search the Catalogue for print-format PEI and Atlantic Canada reports from various agencies and non-profit groups.