You can only see the northern lights during winter time when it’s dark outside (from around late August to late April, often also beginning of May). Also you only see them if it’s cloudless, not raining and not snowing. There is no certain time when they appear the most – they can appear from early evening to early morning. Just don’t forget to look up in the sky frequently when it’s dark outside.
Also check our aurora forecast and cloudcover forecast every 15min to see how big your chances will be. Sometimes they are not very active and you do not see them even on a cloudless night. You also need a bit of luck to see them :).
Generally you can say, if you can see the stars and are patient and staring into the sky for hours, your chances are high that you see some.