Step one: Click on the cog on the right hand side of your calendar and choose settings.
Step two: Click on calendars in the top left corner of the page.
Step three: Choose an existing calendar to share or create a new one.
Step four: Choose the embed code to paste into an html gadget on your blog. You may have to play with the size of the calendar. You can change the height and width numbers. I suggest 255 for the width and 400 for the height if you are going to use it in the sidebar.