SFDC custom object

Hi guys, do you have any experience with SFDC custom object?

I have an SFDC custom object under contacts’ object, and I would like to access the fields under that object in Marketo. I already enable the object/fields under SFDC Objects Sync.

I want to access those fields as attributes and not constrain/trigger. For example, If I have a Marketo field (created in Marketo) and want to copy the values (coming from Marketo) to one of the fields of the SFDC object, how should I do? 

Is it possible?

Thanks.

Andreia