Hi im new! I am very new to all of these things so hopefully someone can help me out

. I have the 5th gen Ipod Classic and I had some general questions about the use of Rockbox on the Ipod.
The Ipod and itunes only allow the AAC loseless file format, but Rockbox allows the use of FLAC. How do you import Flac files into the Ipod then? This is actually my main concern.
If the answer is to convert Flac into AAC. I am completely clueless how to do this. I have a windows and i have been searching for free converters but none work.
Thanks a ton!!