Align Sidebar Content

I searched high and low throughout the forum and while I’m sure it’s likely been addressed on a previous occasion I’m probably just using the wrong keywords in my search.
At any rate, I’m trying to figure out how I would go about aligning my sidebar content centrally as it currently defaults to the left. Images/photos in particular.
In my case, I’ve used the text widget to insert the HTML for a 160 x 600 px affiliate advertising banner.