On official unite web page there is a notion about how to set internet for mobile devices. It says to set APN as

internet3g.unite.md

But this didn’t work for me. So in the end, settings should be:

APN name: Unite Internet Postpaid
APN: internet.unite.md

On android 4 it is set in Settings > (under Wireless and Networks) More… >Mobile Networks > Access point names > (menu) > New APN