Import Groups feature had been moved from Administration > Import to Settings > Groups.
However, the corresponding pop-up help file is missing: uploadgroups.html from group/import.php.
I belive it would be nice to add it back.
Not sure where to report though, here or on the tracker
update: found a ticket MDL-14232
Elena, thanks for pointing out some missing help.
As I mentioned in MDL-14232, as the issue has been closed, I created a new issue for adding the help popup - MDL-26252.
You'll notice that my suggested wording for the help string is more succinct than the old uploadgroups.html, however all the information from the old help file is included in the documentation Import groups, which the new help popup will link to.