The three included actions are Set Cookie, Read Cookie, and Kill Cookie.
Set Cookie allows you to specify a cookie name and a value. Alternatively, you can have the value based on a form element on your page (valid elements are text, textarea, password, and hidden fields). You can also optionally specify a path and domain, as well as a number of hours until your cookie expires.
Read Cookie reads the value (if any) stored under the name you specify, and writes it to the form field you choose (the same types of fields are allowed).
Kill Cookie does what you would expect. Note, however, that if you specified a path or domain when you set a cookie, you must use the same values to kill it.
Instructions: Behavior actions are stored in the Dreamweaver application folder, inside Configuration > Behaviors > Actions. Drop the contents of the archive file into the Actions folder and restart Dreamweaver to access them.