I have just changed my avatar picture as an example, this is how I did it.
1- find an image I want to use, for some strange reason I thought of Albert Steptoe.
2-Google Steptoe and select images,pick an image that appeals and right click on it.
3-In the box that appears left click on save image as.
4- A new box or tab opens and gives you the option to name it as a file name, I just entered steptoe and pressed save.
5- On my system this image can now found by pressing the start button in the bottom left hand of the moniter screen and selecting my recent documents,go down the list and select steptoe which is now saved to your computer.
6-Ok so now starting from scratch bring up the pubs galore forum main page,select settings then select edit avatar.The edit avatar box now appears with option 1 enter ulr to the image on another website, and option 2 upload image from your computer, select this,by pressing the choose file button and a box/tab (I'm not sure of the correct terminology)will appear,where it says file name write steptoe and then press open, the image appears and then all you have to do is then press the save changes button at the bottom and the image will be saved as your avatar picture and appear after every post and on your profile. I know this seems long winded but is not so bad in practice, if any one can explain in simpler terms please do, that took me the best part of half an hour. Anyway hope that helps a little bit Alan, cheers.
p.s I'm not keeping the steptoe thing for long.