If you're using Photoshop, instead of using "Save as" to make a gif, you have to use "Save for web" for it to be animated. In newer versions, this is under the Export menu, and is called "Save for web (Legacy)". Choose gif in the drop-down, and here you can also choose other settings, like how...
Glitter avatar request thread is up! Come get yer glitter avatars! Come one and all!
https://www.tarvalon.net/index.php?threads/get-your-glitter-free-week-avatars-here.31347/