Link your custom app to your Gnome Applications

If you’re running GNOME and you have a custom script/app that you want to be
able to run quickly from your applications bar, you can easily add an entry with
the following:

In your ~/.local/share/applications or /usr/share/applications folder
(choose one depending on whether you want to share with all your users or
yourself), add the following entry:

 # whateverfile.desktop
[Desktop Entry]
  Type=Application
  Encoding=UTF-8
  Name=Sample Application Name
  Comment=A sample application
  Exec=application
  Icon=application.png
  Terminal=false

Modify the Exec to point to the path/file of the application you want to run
and you’re done!

As another example, this is how I linked the
Telegram app onto my Application Launcher
bar.

  # ~/.local/share/applications/telegram.desktop
[Desktop Entry]
  Name=Telegram
  Exec=/home/davidc/Documents/Telegram
  Icon=telegram
  Type=Application
  Categories=GTK;GNOME;Utility;

Reference:

Gnome Developers Integration
Guide