How to make part of an object transparent

For an image object onto which a bitmap file is pasted, you may want to make the white portions of the image transparent. In such a case, you can make the white parts transparent as follows:

1. Select the image.

2. From the menu, select "Tool"->"Paint." The "Paint Tool" appears.

3. Click "Fill with Transparent Color" and then click the portion that you want to make transparent.