Thinking about Rasit's initial post, connecting to networks is so fundamental to the Dragonboard experience that I think we should include a how-to-guide in multiple places, including manuals and FAQ's. I would also suggest that we discuss the use of ethernet USB dongles for those who will not be using wifi.
Rasit, if you have not found it already, in the lower right of the screen is an icon which will allow you to select a wifi access point and enter a password. Left click on the icon which shows two squares connected by a line. You will see a list of current wifi access points in view. Select one and you will be asked for a password.
From the menu in the lower left, you can select Preferences ... Network Connections. This is harder to use for first access to a network. It is easy to use to change parameters, such as a new password for an existing access point.
The aforementioned nmcli commands also work well.