Add the following line to your .emacs:

(require 'eldav)

Using a proxy:

(setq eldav-proxy "http://your.proxy.server:8080")

You can access WebDAV files by preceding WebDAV URLs
with a colon:

:http://your.webdav.server/path/to/file/name

Enabling the Eldav VC feature (experimental):
(setq eldav-use-vc t)