Tvheadend

I would like to test an IPTV link in Tvheadend, but not sure where to start... I'm assuming there are some free IPTV URLs, although not sure where to find them.

I'm assuming that if/when I find one, I just need to enter a URL for the IPTV Automatic Network, and I can take things from there.

Apologies for the haziness but I've never used IPTV before and don't know how to configure it.