I've been trying to figure this out forever. I'd love to upload some of my sims for public use & so that if I want to reuse them later I can. I am using the Ultimate Collection. Anyone know how I can do this?

First you might want to use the Creators Feedback board to get help or tips. https://www.modthesims.info/forumdisplay.php?f=611

Or if you want to upload straight away go up to Create> Upload items. That takes you to the upload wizard. Make sure you read over the Creator Guidelines for sims and that any CC is either made by you or free to use. Your creation goes to a moderated queue where a mod will look over your sim and send you a pm if it has been approved or not or if it requires changes. Good luck!

If these are Sims you created in CAS, you can use SimPE to extract their appearance. Important that you then clone that copy in Bodyshop, and delete the original, as it will have bits of the character still attached (causes corruption if placed in a hood). I'm sure there is a tutorial on how to do this somewhere, if you need it. Maybe someone helpful knows where