Maybe it's just that I've drunk too much booze tonight but I can't make a great deal of sense out of your question. What mail client are you referring to? (Outlook? Outlook Express? Windows Mail? Thunderbird?). When do you find that 'it says edit'?
If it helps at all, here's how to change a default email account in Outlook Express. (It's probably similar with other mail clients):
Go to Tools>Accounts.
Click on the name of the account you want to choose as your default.
Click to place a tick alongside 'Set as default'.
Click 'Close'
If that doesn't help, please post again with a bit more explanation.
Chris