Here's some tips for navigating the format code on the website.
To make a quote box, type quote in brackets - [ ] - paste or type in the quoted content, and end with a /quote in brackets. Sometimes you'll run into issues with copy/pasting text from sites who use embedded formatting code and you wind up with text that's too large or some other type of mangling, so if pasting text, I prefer to "paste without formatting". Any other issues can generally be solved by selecting "Source" and simply deleting any extraneous code which might appear.
When posting images: most social media sites are extremely proprietary about their content and block their images from being posted elsewhere, so it's best not to even try. One way around this is to take a screenshot and post it first to a personal image-site account (ie Pinterest, Imgur, Tumblr, etc) before linking it here. Many 'gif' sites have also been cracking down on these images being posted outside of their platforms. And when posting an image, make sure its url address ends with a recognizable image format, ie "jpg", "png" and I believe "webp" works here as well. If the url is a mile long, it most likely will not work.