Holy Trinity Cathedral is SkyTrain accessible:
Exit SkyTrain at Columbia Station and go down the stairs to the street level from the platform using the southwest exit. Turn right at the bottom of the stairs and go past the ATM and escalator and straight ahead to the Clarkson Street exit. This exit feeds right into a set of stairs - just go up the stairs and you will be on Clarkson Street. At the top of the stairs you will see the Cathedral on your right about 50 metres ahead.
Alternatively, we have very limited parking available in the Church parking lot and considerably more parking along Carnarvon Street. To access the Church lot, you will need to turn off of Columbia onto Church Street and turn left at the end of Church Street onto Clarkson and then right again immediately into the Church lot. In New Westminster, the meter parking is free all day Sundays.
The map below shows the Cathedral as a purple circle and the Clarkson St. Skytrain exit as a blue square.