Once you have uploaded pictures to your gallery and are ready to add to your posts, select the image you want to add.

When adding images to your post you can choose the alignment and size and link to (we will leave that for now) These boxes are found at the lower right hand side of the media library.

If you are adding a picture to the top of your post and you want to center it in the middle select "Center" and "Full Size" See below: this is how it will show on your post.