If you mean add screen shots to your workshop item,
Click on your workshop item, on right hand side under owner controls click
on add/edit images & videos. Click chose files, from your screen shots
shown double click on screen shot you want, click upload. Screen shot
will be added below, repeat process until you have all the screen shots you
want (if added one in error there is an "x" on the screen shot to delete it) click
save and continue. Done. Hope this helps. :)

Yes. this is what I wanted
Thank you very much