Anlage N-Aus is definitely not simply, also if you are not sure, it is better to go to the tax consultants for the first time (in LohnsteuerHilfe Verein). But it is possible, that you don’t need this application at all. Anlage N-Aus – for those who already live in Germany and make some work abroad.
If you are first year in Germany or leave it this year, then you need Anlage WA-Est. it has existed since 2017.
Read about Anlage WA-Est here.