Research can be a big part of your writing, because you want to get the details right. So if you are writing a story about something that happened in the past like the second world war, there is a good chance you need to do research for that. Nowadays a lot of information can be found on the internet, but sometimes you need to go to a public library to get some extra information about something you want to use in a story. Don't be afraid to ask a librarian for help on your subject!
It's also possible that you want to write something about a museum piece that gets stolen for example, so a good way is to actually go to the museum and look at the museum piece, and write down details about where the piece is standing, or hanging on the wall, and where it is positioned in the museum itself. That way, the story gets more believable because people who actually know the museum piece can relate to it.
Reading books about a historical person you want to use in a story can also be very useful. If you want to write about a famous person from the past, there is a good chance you can find many books already written about that person. You can use that information to your own advantage and perhaps rewrite history!
So always make sure you do your research when you want to write about something you need help with!
Happy writing all!