If you’d like to close a session and prevent users from registering on/after a specific date, you can set an expiration date when creating the session itself. Navigate to your Product Management page (Settings -> Products). Locate and hover over your product then click the Edit button then Edit Session. Under the Options tab, you’ll see Availabilty/Expiration Date. Here you’ll be able to set when the system will present this offering to your user.
If you don’t allow partial selections for your session, the session will automatically be unavailable for registration after the start date of the session. This is another way to ensure your session doesn’t show to users on the front end when registering.
If you have a session already set up and would like to remove it from being shown on the front end to users, you can simply edit the product/session to “Admin Only” in the session options, which will not show it to users on the front-end. This can be a quick fix if you aren’t able to set up the expiration and availability settings from the outset.