Checkout extensions
In your Shopify Admin, navigate to Settings > Checkout > Customize, and add both extensions.

Thank you page
This is displayed to the customer immediately following checkout.
Order status page
When a customer revisits the order. Content and functionality wise, the thank you and order status extensions are identical, simply different areas.
POS app extensions
In your Shopify Admin, navigate to Sales Channels > Point of sale > Settings > POS apps > Check In Tickets. Add to Smart grid tile and Additional areas.

Scan tickets (Home tile)
Check in tickets with the camera scanner or external laser scanner. Toggle between lookup and auto check-in modes.
Order check in
Check in tickets from the order details page (no scanning necessary).
Post purchase check in
Identical to the Order check in extension, this is displayed after processing a sale on POS.
Theme extensions
Event calendar (collection template)
Refer to the Event calendar article
Ticket purchase page (product template)
Refer to the Ticket order form article