Don't be put off by it, it really is as simple as Brendan's post suggests.
If you have a photoeditor you can use that to resize the pics before uploading them to P'bucket. Even the MS Office picture manager will do it. But save the resized pictures and then when it asks if you want to save the changes say "no" or you lose the original.
You can also use the P'bucket resizing options when uploading but it is too slow to do more than one or two.
I uploaded a photo yesterday and although it was quite a large image I didnt have to resize it for the forum... maybe it does it automatically from flickr