Sign in to blogger account and then go to the layout page. In the layout page click on the,
Fonts and colors link.
Select the Text Font and then you will be able to see a list of fonts available in the right side.
Select the required font. You will be able to select whether to have a bold text or italic text as well.
Similarly you will be able to change various preferences like Blog title font, Sidebar title font, Blog Description font etc.