To create a User, e.g. a committee member, select Organisation > Admins and Roles
If the Contact is already in the Admins list, you can adjust their Admins 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 add them and give the appropriate Admin Rights.
Sessions Admin Rights
If a Contact has Sessions Admin Rights, when logged in they will be able to see their Dashboard, Sessions and their own Tasks.
Contacts with Sessions Admin Rights would generally be able to view all Sessions and create new Sessions.