And here's the simple guide :
- Go to "Plugins" menu
- Install plugin "display widget"
- Activate the plugin
- on the "Widgets" menu, click options panel for the widget you would like to modify.
- Select "Show on Checked' or 'Hide on Checked' from the dropdown and tick the boxes.
eq: If you want to create a widget that show only on homepage; you can choose Show on checked, and then tick frontpage box.
I've been using this plugin for years. I hope these tips may be useful as well for you.
And like I said in the title, this tips only for wordpress custom domain.