Well, I think both are right.

If you are in Nepal, you have to go to visa extension office.  I think it is in Tripureshwor, but I am not sure.

Alternatively, you can leave Nepal and when you re-enter, you will be given a new visa at the airport.

I am not certain if they issue visa at the land point of entry, such as Kakkarbhitta, Jogbani, Birgunj or Nepalgunj.