Dear, Assessment is not mandatory if you are arrived or got visa but if you do it will help you to get jobs in your field, once you reach here go to Alberta Work, they will get your credential assessed and will pay your fees $110. it takes two months to get assessment letter. keep copies if you need any where to submit for jobs etc. Educational institutions and some regulated profession asks to get your degrees assessed, so it is good to do it as soon as you reach here or even you can do it before landing.
Today I did my driving test and failed, will try again it next time.