How to send notification email to individual users
I just implemented the same thing this morning. I hope my solution will help you, but it probably depends on if your content type field is set up like mine.

My user list is presented via an Entity Reference view that I created. Users check off who they want email sent to and save the content type.

My rule is as follows:

Event: 
    After saving new content

Conditions: 
    Content is of type 
        Parameter: Content: [node], Content types: User message

Actions:
    Add a variable
        Parameter: Type: List of user items, Value: [node:field-people]
        Provides variables: List of members to email (members_to_email)

    Loop
        Parameter: List: [members-to-email]
        List item: Current member (member)

        Send mail
            (contents of email listed here)


You'll obviously have different names for your content type, node field, variable names, etc. but hopefully this will get you started in the right direction. If you want the export of the Rule instead of what I posted here, let me know. I thought that showing you what I did through the interface might be an easier start for you.