ooo, that was so long ago but i’ll try and explain it step by step for you!
first you need to take a screenshot of your town map through miiverse — talk to isabelle and tell her you want to tear down a pwp and she’ll show you the map!
after you’ve uploaded it on miiverse and saved it to your computer you should crop it in your preferred photo editing program — make sure it’s evenly squared too.
it’ll look something like this..
now you go to this site http://www.thulinma.com/acnl/ and convert the image you got and choose the option with 40 colors!
you’ll have something like this which you’ll use as your outline.
now comes the tedious part — cleaning it up. you can either do touch-ups on the site itself like i did or just go right ahead and create a design in-game and do it as u go. it’s good to look back at your map now and then to make sure everything is where it is.
here’s what my map looked like afterwards…
it might look super odd but it will look fine once you’ve copied it into your DS and put it on the sign. hope this was clear enough, i might have missed something so if you have any questions, feel free to ask! good luck!