This post will look at how you center a picture in your blogger sidebar.
Firstly you need to go to Design > Edit Html and tick expand widgets. Secondly search for the text: widgetid='image1' remember to look for a different number as indicated in green depending upon which image widget you are intending to change.
Now add --> align='center' <-- to <div id='sidebar-wrap'> which should be located near the widgetid='image1' text, it is usually below it.
Your line should now look like:
<div align='center' id='sidebar-wrap'>
Now click preview check it works, if it does not click clear edits and consider changing the number in green if you have more than one image widget. Or if it works in the preview click save and your done.