oh look at the blog in edit mode. There should be like a symbol of a mountain in a box that is the picture box. Hit that button with your cursor on the area you want it and it will say "image url" then just paste the url of the image you want. If you don't have the pictures hosted online somewhere and they are just on your computer you need to upload them so you can use the image url feature. 

Use like imgur, just got to imgur.com, hit upload then upload your pictures. Copy the url by right clicking the picure, and slecting copy imgage url.

Anyway good luck and no problem :)