Right click on the pic and select "Save Picture As"

Go to your photobucket account and upload it. You will be give 3 URLs beneath the thumbnail of your pic. Highlight the last one (will have [IMG] tags included), right click > COPY

Go to your PROFILE (top of every PF page) and scroll down till you see the window marked SIGNATUREs. Paste the URL you copied in there, making sure you have the [IMG] at the beginning and [/IMG] at the end all complete, and no spaces....

Then it should show