If you are determined to use DeSmuME specifically, the only verified method is through RetroArch , a free, open-source frontend that uses "cores" to run different consoles.
No official DeSmuME APK exists for Android as a standalone application. While DeSmuME is a gold standard for Nintendo DS emulation on PC, its official developers do not maintain a mobile version. desmume download apk
However, you can still use the DeSmuME engine on Android through "multi-system" frontends or by using superior native mobile alternatives. If you are determined to use DeSmuME specifically,
: Get it from the Google Play Store or directly from the RetroArch website . desmume download apk
: Open RetroArch, go to Load Core > Download a Core , and scroll to find Nintendo - DS (DeSmuME) .