To create your own button, you need to be signed in to Yahoo!. When you're signed in, click the "Pencil" button (it has a small picture of a pencil on it) and choose the "Add/Edit Buttons" option. Then select "Your Button."
You will see a "Change Layout" button on this page. Click this button if you want to rearrange your buttons on the toolbar.
Remember to click "Finished" to save your settings. You should see your button changes soon after.
Locate the "Your Own Button" on the Yahoo!7 Toolbar and then follow the directions below:
The toolbar refreshes automatically to show your custom button with your new button title and icon.