You can Add manually installed application to ‘Show Applications’ grid in Ubuntu by creating a launcher for the application (.desktop file) in your ~/.local/share/applications directory.
If you want the application to be available to all users, you can put the .desktop file in the /usr/share/applications directory.
First create an empty text file, name it something like <application-name>.desktop, and add the following lines to it
[Desktop Entry]
Name=Application Name
Comment=A short description of the application
Exec=/full/path/to/application/executable
Terminal=false
Type=Application
Icon=/full/path/to/icon-file