I got this information from
this thread and cleaned it up for clarity and ease of use. Credit goes to Golds and dsrules for posting the info in the first place.
These steps worked for me on a G6 lite with firmware version 4.6a, and Dipstar 5.12FF. I don't know if it will work with earlier versions of either.
1. Get the current version of Dipstar and unpack it.
2. Copy 'dipstar.ds.gba' to the G6. Do not use the U-Disk software, just copy the file. I put it in the root folder for easy access, but any location on the cart is fine as long as you remember where you put it.
3. Load the NDS game onto your G6 with the U-Disk program. You can use any read method that works for the game EXCEPT safe mode. Safe mode will not work with dipstar.
4. Inside the Dipstar .rar file is a program called m3dip.exe. Select the NDS file on your G6 cart that you want to use dipstar with, and drag it onto m3dip.exe. Push enter when prompted.
5. In the NDSMode menu (press start) go to 'MyCard', and then to the location of the 'dipstar.ds.gba' file you copied
earlier. Highlight 'dipstar.ds.gba' and Press X once. When X is pressed, the loading circle will appear for just an instant.
6. Go to back to the 'NDS Game' menu and select the game you "dipped" with m3dip.exe.
7. Press A, then immediately hold the L button until the Game Boy into screen pops up on top of your NDS G6 menu.
8. Choose a button to set the codes to, then press that button. Remember which button you used, you will need to hold this
same button when you load the game in order to use the cheats.
9. Enter your Dipstar Codes, then push start to save them.
10. Turn your NDS off.
11. Turn your NDS back on.
12. In the NDSMode menu, go to 'MyCard' and then to the location of the 'dipstar.ds.gba' file you copied earlier. Highlight
dipstar.ds.gba and Press X once.
13. Go back to the 'NDS Game' menu and highlight the now coded game. Press A, then hold the button to which you saved the
codes until the game is loaded.
edit: Fixed steps 3 and 4.