Elizabeth,
That doesn't seem possible before I've actually synced Marketo and SFDC.
I see the screen you're referring to on my live account, where I've already synced, but not on my Marketo Sandbox account, where I haven't. Below is what I see in my pre-synced Sandbox account;
![0EM50000000QN0h.jpg 0EM50000000QN0h.jpg](/t5/image/serverpage/image-id/4983i6793E65D2DB891AA/image-size/large?v=v2&px=999)
It's not clear what to click on to get visibility on which SFDC account is linked.