You need to have access to the needed tables to create a connection to the database and then create a tableau visualization on top of it.Please get access from your DB administrator and then proceed.
Alternatively you can use excel sheets also.Please check on whatever is feasible in your case.
hope it helps.
My question is specific to Impala connection, I've access to Impala DBs and Tables, able to access them through Hue editor.
But it's blank in Tableau connection window, here to confirm whether I miss any connection configuration.
Hope I made it clear.