Long story short, I'm an idiot with no technical skills but I want to make a 3DS theme. I have the FLAC file of a song I want to use. Obviously, I can't use the FLAC file (it's not supported, I'll need to convert it to ogg and there's also a filesize limit I'm sure), and I don't want to use the whole song anyway. I want to have it open and then loop the refrain indefinitely, but I don't even know where to begin. I'm using audacity but if there is a better software to use, I'll switch.

Please walk my dumb ass through it