After you install desktop Environment, the internet connection still do manually, to make auto with GUI configuration, i usually using networkmanager. Because it's easy to use.
Open terminal, then install
#pacman -S networkmanager network-manager-applet
Then to enable it
#systemctl enable network.service
Then try adding networkmanager applet. You should find nm applet icon on system tray. Here's the snapshot:
For some example of usages:
Right click on Network Manager, then click on Edit Connections, to add new connection.
And here's The GUI menu of network manager
You can set wired For LAN connection, Wireless for Wifi Connection, Mobile Broadband for some USB modem devices, VPN, and DSL. In my connection i usually using wireless, and usb wired connection. For others i didn't try it yet on network manager.