Setting a bundle to private will make the bundle available via direct link only. This means the bundle will not appear on the catalog page for your viewers to access it. The only way to view the bundle is through your invitation.
To make a bundle private:
Navigate to Bundles and click Edit to change the bundle you want to make private
Scroll down to Availability and toggle Private
Click Save to apply the changes
To get the direct Share Link of your private bundle:
Navigate to Bundles
Find the Bundle for which you'd like to obtain the share link, then click on the ellipsis (three dots) to the right of the Edit button
Click Copy Link
Then click the Copy button on the pop-up window to get the shareable link