When working with a page or web feature in CMS you will have an Advanced tab with a Security Options section.

Expand the Security Options section to set your security requirements for that page.

The following are your selection options:

Use Web Site Default    - inherits restriction settings from website.
Anyone can access web page  -  places no restriction on this page.
Every contact with a login in your account will be able to access web page -  only requires that the contact have a login in Sphere.  Does not specify where that login is associated.
Membership required to access web page:  - requires login with the specified membership attached.
Event Login required to access web page:  -  allows you to base access on participation in event(s) you select.  Multiple selections encompass the logins from multiple events, and does not mean the participant has to have a login to ALL of them (participant in Event 1 OR Event 2 OR Event 3).