Goto your workshop item page and click on add/edit images and videos.

yes and sketchfab?

It is inside.

inside what?
how to use sketchfab with brick rigs?

Inside the add/edit images and video link.

The workshop is a steam feature, a repository for files for games, brick rigs doesn't have anything to do with sketchfab. I think sketchfab is supported by steam to give users a way to display models in their workshop pages. As you can see if you look they are looking for links, not uploads.

i wondered if the brickrigs models are compatible with the skeetchfab format that accept many diferent
what is the brick rigs format ?
where the brick rigs file are located in folders ?

I think all of brick rigs contents are in pak files, i don't know if you can extract content from the pak file, at least without the right tools.

There are obviously modders around, you would have to ask one of them about it.

as you know well all the skilled people never are in this forum or are complete antisocial parasits and probably psychopaths with severe mental troubles

They still have accounts, workshop pages or guides all with comment sections.

and are of no help or worst are pure trolls

There may be information in the wider community as a whole about pak files, use the community search.

im still at searching how to use timers loop before focusing on secondary task
it was just for check if it was common