You’ll want to hop on the Northern Line (black line) on the London Underground. You’ll need to head towards the Edgware branch and get off at the Brent Cross station, which is the closest one to the shopping centre.
Once you’re at Brent Cross station, it’s about a 10-15 minute walk to the shopping centre. Just follow the signs, or if you’re not up for a walk, you could grab a quick bus or a taxi from the station.
If you’re coming from central London, you can catch the Northern Line from major stations like King’s Cross, Euston, or Camden Town. Just make sure you’re on the train going towards Edgware and not the High Barnet branch, as they split off at Camden.
Hope that helps! Let me know if you need anything else.