Communication between editors takes place at Talk pages.

To send a message to another editor:

1. Go to their user Talk page (e.g. User talk:xxxxx)
2. Click the "Add topic" button at the top and, when the editing window opens, you can type your message and a subject heading to your post.
3. At the end of your message, include your signature with ~+~+~+~ (~~~~ four tilde characters).

Note that user talk pages are publicly viewable, so it is not a private message to the user concerned. Even when deleted, the message is forever viewable in their History.

Editor replies: Unless the other user includes a link to your user page in their reply (called a Ping), you will not get a notification that they have responded, so it is a good idea to either check their talk page every now and then, or add it to your Watch list.