Hia,today I am gonna tell you how to change your theme on your blog:)
First you have to make your blog,and when you are making it you will have to chose some theme(if you dont like it you can change it).Ok,when you are done making your blog go to Scrap-e-blog.blogspot.com :)
when you go to it you will see so much different themes and some codes under them.When you chose the theme you like copy the code that is under that theme and go to your blog.Chose "new post"and just paste that code in your post.When you publish that post your blog will be in the theme you chosed:)
I am happy that I helped you if you didn't know how to do that:))