WooCommerce → QR Tickets: enter the event name, date, time, venue, address and dress code, upload a logo and pick your colours. Save.
Products → Edit a product (a Virtual simple product is ideal). Open the QR Tickets tab, tick This is a ticket, set Seats per unit (1 for a single admission, 8 for a table of eight). Save.
Place a test order. When its status becomes Processing or Completed a ticket is issued, the ticket card appears in the customer email, on the thank-you page and in My Account → Orders, and the ticket is listed under WooCommerce → Tickets.
At the door, staff log in on their phone and scan the QR code (or type the code at https://your-site.com/ticket/). The check-in panel appears below the ticket.