Remove the MicroSD card from your R4 flashcart and plug it into your computer using a USB adapter.

To get started with the R4 theme creator, follow these steps:

Turn off your Nintendo DS and remove the MicroSD card from the R4 flashcart.

For complete creative control, template-based manual editing is the preferred method for modern creators.

For modern DS homebrewers, has become the gold standard. It supports highly detailed, DSi and 3DS-style themes. While it requires slightly more file management than a classic R4, there are numerous example templates provided by the community that serve as perfect starting points for your own designs. How to Create and Format Your Own R4 Theme

The stock R4 does not support custom fonts. However, allows a cursor.bmp :

Save your theme folder and drag it into the _system_ or themes folder on your microSD card.