It makes less sense in English, because English only has "you" for the 2nd person. You can say "Sie" to another person (polite, usually people you don't know, older people, boss,...) or "du" (informal, friends, family,...). It should be more like: Wir können "du" zueinander sagen. It means they use "du" (Wir duzen uns) instead of "Sie" (Wir siezen uns). And that's why they use their fist names and not their family names afterwards. Maybe you thought it means something like "Wir können miteinander sprechen. Wir haben uns viel zu erzählen." Hope it helps. :-)

We can say "du" to each other. Du is informal. They are giving permission to use the informal du when speaking in this group of people. When I started speaking with German friends on italki, I was told the same right off the bat - because I was using the formal "sie" with them. I said, Wie geht es Ihnen? And he said, we can use "du".