If you are a member of this blog you will find it listed on your personal blog page that you get to when you log in. The page at my blog.co.uk is the one you want.
There is a little box on one side entitled My Groups.
In there is a link to Powercats - which is the Powercat Owners Group.
Alongside the Powercats link are a series of little icons.
One of them is a pencil and that is the place to click to write your own blog post to the group.
Once you have clicked on the pencil, you get to the 'old editor' which I don't use because it's for people who know html and clever stuff like that, so it isn't for me. I click on the blue words at the top corner which say something like click here to beta test the new editor.
Once in the new editor there are boxes at the top edge.
The group of boxes labelled Insert media: are the ones we are interested in.
Here you can use the box with a green up arrow - to upload your picture from your computer into the blog media storage from wher you can then place it onto the blog, using the picture of the magnifying glass looking on a yellow file box.
Or you can store your picture at tinypic or some other image storage host like flickr and then once you know the url for it you can use the picture with the tree and follow those instructions.
I don't know how to use the box with a picture of a ladder/window/piece of movie film - I am not even sure what the icon is.
So any member of the group who has joined can write a post using the pencil etc and then upload image via the write post screen.
Hope that makes sense. I think its right. Good luck.
