1. download drastic emulator on your android device either through your android browser or pc via this link https://modapkdl.io/drastic-ds-emulator-apk/
1.2. Enable “installation from unknown sources” via settings-device-security to be able to install drastic emulator and any other app from the web.
2. install drastic emulator using EZ file explorer or file manager on your device (to install drastic emu full paid version from above link your device must be rooted) separate tutorial via this link: https://www.youtube.com/watch?v=u3nzF-OI5D8
3. download your desired nds roms from this link https://www.downloadroms.io/roms/nintendo-ds/ on your pc or via your android browser
3.4. if using pc to download roms make sure to have winrar or 7zip installed to be able to open and extract the roms from there folders. https://www.rarlab.com/download.htm or https://www.7-zip.org/download.html
4. create a folder on your android device to store your roms in using EZ file explorer or your pc and move the roms you’ve just downloaded into that folder you just created.
5. launch drastic emulator on your device and click load game the emulator will scan your device for roms and a list will appear from there just click and play.
NDS Emulator and Roms setup Android Tutorial (EASY)