There is no formal appeal process. However, if you believe the visa officer made a legal error, you can send the details to the following address:
Immigration, Refugees and Citizenship Canada
Jean Edmonds North Tower
300 Slater Street, 9th Floor
Ottawa ON K1A 1L1
In some cases, you may seek a judicial review by the Federal Court of Canada. This is not an appeal on the merits of the case. Rather, this review examines the process that led to the decision, to see whether the process was fair and reasonable.