iTunes updated to the latest version 18.104.22.168 and I don't know how to sync my songs that I've put on
Same way as before.
Do you have the sidebar showing? Go to iTunes>View and click on Show Sidebar
My iPod is connected to the computer and it's charging but doesn't appear my device on iTunes,
iOS: Device not recognized in iTunes for Windows
iPhone, iPad, iPod touch: Device not recognized in iTunes for Mac OS X
If a PC I would start with
Removing and reinstalling iTunes, QuickTime, and other software components for Windows Vista or Windows 7
Removing and Reinstalling iTunes, QuickTime, and other software components for Windows XP
Retrieving data ...