I have a Mac - version MacOS High Sierra. I am an 'oldie'. I wish to add an additional email address in Mail {to enable me to register with a new Doctors Practice as well as my hubby] but cannot as I am told that the version is not secure enough. For years I have shared my husbands email address [neither of us are technically trained or minded]. I have attempted to update my Firefox version but cannot do so as my menu does not show the 'About Firefox' option from where I hope to begin. Can anyone please advise me how I can update Firefox plus add an additonal email in my Mail option. Fairly simple instructions would help. I would appreciate any assistance that anyone can give please.