It depends on how recent seahorse is. For a sufficiently old seahorse you could just copy the given keyring files into the new ~/.gnome2/keyring directory. For a more recent seahorse you would copy the keyring files into ~/.local/share/keyrings.
Recent versions of seahorse are annoying in that you have to explicitly go to the view menu and state that you want to view by keyring or it will only show passwords for keyrings that are already open, but once you do that change it should work. Before I figured this out, it looked as if seahorse wasn't seeing the key rings.