How can I make an analysis of John Donne's "For Whom the Bell Tolls"? What is his main message of the essay, and whom he is addressing it too?

You might center your analysis on the the three analogies
that Donne uses in his sermon to a congregation:  the book, the bell, the island, and
gold or treasure.  In your discussion you could show how each shows the speaker's faith
in God and his belief that all men are connected:  "No man is an island."   These
analogies, or conceits, are trademarks of Donne's writing.  As you discuss each of these
analogies, you should show how it connects to the main ideas of the essay (faith in God
and interconnectivenss of mankind) and why the analogy is appropriate or effective in
conveying these ideas.