Once the connection is set up and authorised you can make calls against SalesForce in exactly the same way as you do against a SQL database. This includes calling custom tables that you add to SalesForce.
One thing to watch is that you will need to log in to SalesForce using a browser on the machine that you will be running Qlik Sense on. If you are running Enterprise you will need to RDP to the server and login to SalesForce from there. That is a one off thing, and then SalesForce will be happy with that machine.
Hope that helps,