This update support 3DS2.1 and DSi1.4.3. Please refer to readme file in the package.
Please choose update file according to your console. If you're using DSi or DSXL please use ak2ifw_update_3ds21_DSi14 3.nds to update.
I f you're using DSL or DSPhat please useak2ifw_update_3ds21_DS i143_onDSL.nds to update.
Just follow the instructions after you run the update file.