For federal directors, candidates apply to a selection process via the Privy Council website. A selection committee then undertakes evaluations for the minister's consideration, and the minister then recommends a candidate for a Governor in Council appointment. The recruitment for user directors is managed slightly differently. It's managed by each Canada port authority through their user nominating committee. Often they will do a similar recruitment process, but it may vary. The committee then identifies candidates for the minister's consideration and makes recommendations to the minister. Then the minister recommends candidates to the Governor in Council for appointment.
We would note that in addition to this, federal candidates all have to go through security clearances as well as the interview process before the recommendation is made to the Governor in Council. The Governor in Council makes the appointment.