If a participant only wants to purchase a ticket to a specific workshop and not the whole event, they simply have to go to that session and click on the Buy Ticket button. To create a ticket type and display the Buy Ticket button on a specific session's page, you need to do the following:
Go to Tickets & Fees > Tickets & Fees Setup to create a ticket type under the heading "Selling tickets for workshops?".
Then, go to Program Builder and edit the session which you are planning to sell the tickets for. In the session editor, select the ticket type you would like to associate with this session / workshop. Click save.
The "Buy Ticket" button would now display on the Session's information page. Users can click on it to purchase access to just this specific session.