Create a custom Application icon on Ubuntu

Create text file like below:

[Desktop Entry]
Type=Application
Encoding=UTF-8
Name=MyApplication
Comment=My fancy new application
Exec=my_application
Icon=my_application.png
Terminal=false

Name it as YOUR_APP_NAME.desktop, and then put it into /usr/share/applications for anyone; or put it into ~/.local/share/applications for current user only. Then you will see it in the Applications list

Ref: https://askubuntu.com/questions/1026528/adding-custom-programs-to-favourites-of-ubuntu-dock