Changing sef without losing old one

[v 1461]

Hello
I haven't changed my online sef since June 2015 ( old version). In the last 2'years I only did it on a paper .
The problem is that I am not sure where to press without loosing all the writing of my old sef.
Every time I try to change it it says that I will loose my old sef and I do not want to have to start from scratch again.
Could you please let me know how I could use my old one and do some copy and paste if possible , where to press on their web ?

It has probably been explained on a different post but I can't find anything.
Thanks
V