Welcome to garden.org,
@jillmckelv !
My one and only experience with a compost tumbler (many years ago) was quite a disaster... I think I was pretty much only throwing in the veggie trimmings and such, and no "browns," which are drier, and it all turned into a nasty, smelly mess
Like Daisy, I also use a small lidded bucket (from ice cream) to store the scraps, then take it out to my compost pile every few days.
I hope someone will have some better info for you -- but I would say put the "brown" material into the tumbler, then just start adding your veggie scraps as they accumulate. If it seems like things are getting too wet, add more browns.
