I think you won't be able to import the tables as synonyms in Integration Studio, but you can import them using their original names, and then change the "Table or View name" to the synonym.
That being said, I can't imagine a reason why you would want to use the synnym in an extension.

Hi Joao,
Actually I am trying to create extension in integration studio, due to some security concerns business was unable to provide owner credentials of tables present in Oracle database instead they have provided me credentails of user who have read only access on those tables(we can query tables but those are not physically present in list of tables as provided in above screen) . Hence we are trying to use synonyms for those tables, Kindly help me in this situation to create extension.

afaik it's possible as long as you have enough rights on that schema.