How do I display a bitmap on a button?

You can use a bitmap or an icon on a button, although an icon is a better choice, as icons support transparency.

This example code sets an icon (from the resource file) onto a button control in a dialog:

BOOL CMyDialog::OnInitDialog()
{
	...

	HWND hUpCtl;

	/* The button is control IDC_UP */
	hUpCtl = GetDlgItem( hDlg, IDC_UP );

	/* The icon is IDI_UP in the resource file */
	HICON hU = ::LoadImage( AfxGetResourceHandle(),
			MAKEINTRESOURCE( IDI_UP ),
			IMAGE_ICON, 0, 0, LR_DEFAULTCOLOR );

	::SendMessage( hUpCtl, BM_SETIMAGE, IMAGE_ICON,
			(LPARAM) (DWORD) hU );
	...
}