Zipit 2

I have the Zipit 2.How can I IM to someone elses Zipit? I don't always see my IM friends under the "MyFriendz" column. Do they have to be online in order for me to see their IM names listed or should their IM names always show on my list even though they aren't online or on their zipit? The only names I see all of the time are those who I can text to their phones. For instance I set up an IM account in Yahoo for my niece so she can use her Zipit. I can't send her messages to her Zipit because her name doesn't appear on my "MyFriendz" list. Same thing for her. She can only text to someones phone and not to a Zipit. And yes I did add her and she added me. I do however see all of those I've added both text and IM frinds when I click on "Delete My Friendz". They are all there so I know they are added. Please help!