you can't, really, any more than you can edit a letter someone's sent you in the post. But if you then forward it to yourself, the text becomes 'live' again and you can change it before clicking on Send.
Do you mean copy a bit of it, paste it into something like Word to edit it, and then paste it back into an email?
To copy some text highlight it, right click and select COPY
As above, why would you want to edit something sent to you... unless you want to send it on to somebody else, in which case just select forward on what ever you use for your mail and you'll be able to edit it before sending it to somebody else.
you can't, really, any more than you can edit a letter someone's sent you in the post. But if you then forward it to yourself, the text becomes 'live' again and you can change it before clicking on Send.
jno right go into forwarding then you can "cut bits of text out
i do this when forwarding "funnies" to my friends not wanting to give out where its come from etc,