diff --git a/README.md b/README.md
index 649df7a..e4c10f9 100644
--- a/README.md
+++ b/README.md
@@ -16,3 +16,19 @@ $ cd vw_mmc-tools
 $ chmod +x mmc
 # and after that you can use ./mmc command, you have to read forums depending on your nav system.
 ```
+# Updating the maps on RNS315 (THIS GUIDE IS FOR RNS315 ONLY, IF YOU DON'T HAVE THIS NAVIGATION, YOU MIGHT END BREAKING YOUR SD CARD, IF YOU HAVE OTHER SYSTEM, SUCH AS RNS310 READ OTHER FORUMS)
+
+Steps:
+Extract the content and copy on the SD, top folder is navpsf_update
+Look under /dev  to see which SD is yours, in my case it is mmcblk0
+
+Change the CID with the attached tool
+sudo ./mmc prog_cid /dev/mmcblk0 5d53424c32424d31013917ca53010400
+remove the card and reinsert it
+
+Now lock the card by password, it's not possible to unlock it with normal MMC
+driver, you need a patched version of kernel to be able to unlock it. Password
+you know from command below.
+sudo ./mmc lock_sd /dev/mmcblk0 C99A20843ED7D90B6801E49F2BC80277
+
+Enjoy your new maps!