To create a Friends Mode League, you'll start by clicking the 'Friends' tab at the top of your page. From there, you'll click the green 'Start My League' button at the top right corner.
From there, you can pick your sport, name the league, and upload a league avatar! Once you've done all that, you can select your contest size, entry fee, and how often you want to play. Don't worry, you can change these later.
Finally, you'll want to invite your friends! You can invite them by entering their FanDuel username or by sending the link via email. You can add or remove friends from your league at any time.
For more information about Friends Mode, please check out this page.