Generally there are 2 common ways to add pictures to your blog:1. Upload an image from your computer.
2. Copy an image URL (or web address where that image is located).
I tend to caution against the "Copy URL" because in the event the creator of that website ever takes the picture down, you will then lose that picture on your blog post. Instead, consider finding a picture you like, downloading it to your desktop and then uploading it to your post.
1. Google an image you'd like. Right click on the image, choose "Save Image As".
This pops up a box, make sure you click on the right hand side to choose "Desktop" as the location for which you'd like to save the photo. (Otherwise it gets lost in the abyss.)
2. Go to your blog, click to make a new post, then click this:
(it's on the toolbar when you're writing a post)
3. This pops up a window where you can choose "Upload": "Choose Photo" and you'll click on your desktop, and locate the picture you just saved.
By default, blogger will stick your image smack in the center of your post. Notice when you click on the image you will have some choices (Small, Medium, Large/Left, Center, Right) etc. Play around with those to have your image located where you'd like and the size you'd like.