First: Get the last firmware, you can find it in the download database
Here one guide how to update (It's not by me, i've found it at the download database. )
Important: This upgrade need to format N-Card, please backup your games and saves first.
1.Insert the Writer into slot 2 and insert N-Card into slot 1.
2.Use USB cable connect to PC USB port directly. (Please do not use extension USB cable)
3.Hold the "up" directionnal button and turn on power.
4.still holding "up", press "L+R+A+B", will enter upgrade mode(red color text).
5.Double click "NAND_ALL.bat"to run upgrade program. Please ignore if there some "found a badblock" appear when upgrade some 8G dslinker.
6.Quick Format N-Card by holding DOWN+A+B+L+R when starting your DS.
7.Copy "xmenu.nds" to the root (main directory, i.e. N:/ )
8.After the first time enter "GAME MODE", DSYSTEM folder will be set up. This folder you must not delete, or you will get an error when starting.
Now your N-Card/Clone should be updated ;D