Daft How-To-Use-Flickr question

[Nik da Greek]

I'm hoping some of the long-term (and/or wiser) Flickr users might be able to help me out here... I joined there when Photobucket started self-harming but I've never seemed to be able to get up to speed with how some of it works... I always just dumped my pics and left them but Flickr seems much more of a community-based thing. I take hundreds of photos of cars at shows and such, and keep getting requests from such-and-such Owners Club to add a photo to their group

How? (and not in a Fred Dineage way)

Do you actually have to join their group to do so? No disrespect, but I don't really want to end up in loads of groups of beardy BSA enthusiasts counting rivets or arguing about what the correct sort of footpeg rubber was for 1954... y'know, the specifics of it all that we all obsess about but no-one outside our chosen marque gives a four-X about

Any advice gratefully received

[Nik da Greek]

So there's no simple way of doing it without joining the relevant group then? Sounds a bit... well... time-intensive