The overall dimensions of this grouping in Blue need to be defined by you.[ leave the default values , change it later on]
Replace the part in Red with the link/URL of the picture
Now click the button and paste the code modified by you.
Click on button again to preview the picture with the overlaid text.
You can make changes to the size of the picture by dragging about the borders around it.
Also drag the borders around the text to change the its settings and size. Use the blog editing tools give by msn spaces to get your desired Font and size / style of font.