private messaging help

hi, we have installed a test website, to test out the membership plugin and also the private messaging plugin

not sure if you can advise how to best test the private messaging plugin, to how i need it to work for the client

the client is a personal trainer who will be offering online training to clients who sign up on here website, she needs a convenient way to chat and send items to her clients including

weekly documents, video links and just general chat

what I need from the plugin is the following

1. way to record any previous chat and conversation
2. quick way for my client to start a private chat with any of her clients
3. quick way for her clients to be able to send a quick message to her or reply to her message

i don't quite understand how the send to part works and how it would work like how I need it above?