“Your Excellency” or if he happens to be a cardinal “Your Eminence”.
Now, as a practical matter, many people will simply say “Bishop”, “Archbishop”, “Cardinal”. Actually, even “Father” is appropriate.
Now in letter when addressing an envelope, for instance, one might go with the most formal “The Most Reverend Archbishop Thinkshessoholy D.D.”
Then, you could always just refer to him informally as “Bub”.
As far as ring kissing, it can be approrpriate but isn’t required. Some people like to do it (especially in a more formal setting) and some bishops like it, but probably no one will complain if you don’t. It certain situations, attempting it can actually be quite awkward.