[Ti] [for sure OT] picture in Mail

[Dr Trevor J. Hutley]

I put (my) picture in Mail, so that it is at the top of each email.
Now I want to change it or remove it, but cannot for the life of me  
remember how I put it there so how to remove it or change it.
HELP in Mail or in the Knowledge Base seems to give no answer.
Can anyone who remembers the procedure just remind me, or tell me  
where to look??
Thanks, and sorry to trouble the List, as this is not specifically to  
do with my Al-book, although I only have an Al-book so it seems on- 
topic to me....

TREVOR