How to Connect to Salesforce
Connecting to the database will require to enter the host, port, database user and password as explained in the Connection Dialog.
How to Setup a Work Environment
Salesforce is a cloud database. You can start a trial on https://login.salesforce.com/. After login you need to reset the security token. For this press the personal profile icon.
Then use 'Reset Security Token'. You will get the token per email. Details also on https://help.salesforce.com/articleView?id=user_security_token.htm&type=0
When connecting from DbSchema you will have to set in the password field the regular web login password concatenated with the security token.
Salesforce uses in the backend a relational database. A nice tutorial is https://www.tutorialspoint.com/salesforce/salesforce_overview.htm. The tables can be found in the Objects Manager tab.