To create a Admin, e.g. a committee member, select Organisation > Admin and Roles
If the Contact is already in the Admin list, you can adjust their Admin Rights by selecting Edit Admin Rights and clicking on the appropriate check box item to unlock it - or, give them the permissions for that level.
If the Contact isn't yet a Admin, you can Invite them and give the appropriate Admin Rights.
Pages Admin Rights
If a Contact has Pages Admin Rights, when logged in they will be able to see their Dashboard, Pages and their own Tasks.
Contacts with Pages Admin Rights would generally be able to view all Pages and create new Pages, Menus and External Link items.
If the Admin is required to maintain the Public Facing Page in addition to the Pages, then Settings Admin Rights also needs to be applied.