You have two options.

1) Go to 'Create Game' on the multiplayer tab and search for the username of your friend.

2) Get Muli's Userscript (https://www.warzone.com/Forum/106092-mulis-userscript-tidy-up-dashboard) and use the added search function to find your friend.

Where is the search function? I use Muli's but don't see it.

No, no, no, it's all wrong. He wants you to be his friend :)

ill be your friend :)

@krinid you have to be on multiplayer dashboard for the search button to appear.