How to make video on blog post page smaller than full width

Okay, this is a blog issue, not a page issue. 7.1 blog post pages do not have Fluid Engine so they work a bit like 7.0. I will start from scratch. You edit a post and maybe a section.  To add a  block you hover over a text block (and one may pop up on its own) or any other block until it gets a blue frame and + signs on the top and bottom. You click one of those + depending on where you want the block, in your case a video block. Add your video, like you would any other page on your site. Now comes the fun part. You have to use spacer blocks on each side of the video block to size it. You add them one at a time. You add one then drag it over to one side until a vertical blue line appears but you don't want that line to go up any further than the block or it will shift your whole page to the right if you moved the spacer to the left side of your video block. Once you have one positioned correctly add another one, position it, and then resize the blocks to push the video block to the size you want it to be, it will keep the same aspect ratio. Don't forget to hit done and save (yes I have forgotten).