Go to http://steemitworldmap.com. Search for your location, click on code (down the bottom) and add a short description. It will then generate the code you need to copy and paste into your post (not the comments) to have it show up on steemit worldmap. Then your post will be on the map! There’s also a FAQ section if you need it.
You can only add posts that are still within the 7 day edit window to the map.