Hi,
you can do this with a CSS code, try to add this code in your template options

.createdby span{display:inline-block}

.createdby img.avatar.author_avatar {float:left;margin:0 5px 0 0}

NOTE: it's possible that this code does not affect the image because it may be not vlid for all templates, if it's so then please post me your site link to allow me to see your article page.

TNX