How do I get from Union to Dundas at Eaton Centre?

From Union, I go northbound on the subway. Last time I took the finch northbound, I ended up at Dundas but had to walk across the street to Eaton Centre. I know there's a station right at Eaton Centre. How do I get from Union to the Dundas station so I go straight into the mall? Do I have to take the Downsview northbound?