The first dropdown in the Details > Permissions tab let's you determine who can see and signup to your event. Would you like your event to be public, visible only to logged-in volunteers, or only anyone you send the link to? If the event is Public, it will appear in your Hub when you publish it. If you set the event to 'Community Members Only', volunteers will only see the event in the Hub if they are logged-in and a member of your directory. 'Anyone with the Link' means the event will not appear in the Hub at all, and will only be visible to those people you send the URL to.
You have two options for applications: manually review and accept/decline them, or automatically accept all. 'Automatically accept applications' is a great option for activities that don't have much of a review process. If anyone can signup, you may want to consider automatically accepting applications.
Like with application management, you can choose to manually review and confirm shift requests from volunteers, or automatically confirm all requested shifts from volunteers.
When you automatically accept applications and automatically confirm shifts, the shift signup list will update in close-to real time, meaning that volunteers will be able to see which shifts are still available as others signup.
If you choose to manually review and confirm shifts, the shifts will appear in the schedule as 'requested' shifts that require your confirmation. Whichever scheduling options you choose, you will want to notify volunteers of their confirmed shifts as soon as possible.