Multiplayer Settings

(1) On the Free Flight map, click Flight Conditions

(2) Choose Custom for weather and time. Pick whatever time of day and weather you want.

(3) Make sure Multiplayer is set to All Players

General Settings → Online

(1) Enable Multiplayer

(2) Set mulltiplayer server to West USA

Settings → Graphics → Global Rendering Settings → Air Traffic: Anything but OFF. 

The higher this setting, the more unique planes will be shown in the game.

To see the names of other players in game, you need to turn on Traffic Nameplates. You can do this in Settings → Flight Interface.

If you have a keyboard, the default shortcut for Toggle Nameplates is ALT+2.