The easiest way would normally be CSS animations, but you can't do those in cohost due to the <style> tag being locked out. There are a few built-in animations that cohost has which you can tap into (I think there's a post about it if you search in the css crimes tag), and there's also the option of using SVG animation. Prechoster has some tools to help you convert a CSS animation into an SVG animation and then convert that to an embedded SVG that you can copy-paste into a cohost post.
Sorry if that's a bit obtuse and not helpful, but I'm very sleepy and I hope that at least helps a little bit. ^^;
