Got this one from ddg images but I think it was posted on reddit by someone.

Save the image to:
/.local/share/icons/

Save the modified .desktop file to:
/.local/share/applications/

This is mine, including the execution command modifier to make the window frame adwaita dark for gnome:

[Desktop Entry]
Name=DOOM Emacs
GenericName=Text Editor
Comment=Edit text
MimeType=text/english;text/plain;text/x-makefile;text/x-c++hdr;text/x-c++src;text/x-chdr;text/x-csrc;text/x-java;text/x-moc;text/x-pascal;text/x-tcl;text/x-tex;application/x-shellscript;text/x-c;text/x-c++;
Exec=bash -c 'GTK_THEME=Adwaita:dark emacs'
Icon=doom-emacs.png
Type=Application
Terminal=false
Categories=Development;TextEditor;
StartupNotify=true
StartupWMClass=Emacs

and one I made for the Terminator terminal