Board METRO Expo line from Santa Monica Station to 7th MC. Transfer to Redline Or Purple line East to Union Station.. Have a safe trip..
Easiest way , find where you can catch the line 704,runs along Santa Monica Blvd it will take you right to Union Station, also you can take line 733 runs along Ocean Ave, I think, and then along venice blvd, if you wanna take the train just take the expo line to downtown LA, then at the end of the line at 7th/metro transfer to red or purple line going to union station.
Thanks! Your answer is awaiting moderation.