tell of (something)
To relate information about something (to someone). A noun or pronoun can be used between "tell" and "of" to specify whom the speaker is telling. The book tells of catastrophic events that befell the earth thousands of years ago. She has been telling us of her research into new treatments for degenerative neurological disorders.
tell of someone or something
to speak of someone or something. The messenger told of great destruction, hunger, and disease in the northern part of the country. I want you to tell of Jane and how she is doing.