http://www.gnupg.org/
Once you get it, generate your personal key pair. Keep the private key on your computer, and don't give it to anyone (they don't need it.) But make your public key known to anyone you care about. Then other people can encrypt messages using your public key that only you, using your private key, can decrypt.
If you use Thunderbird for email then it has a plugin for GnuPG. If you use something else, or a webmail like Google, then you can decrypt just by copy and paste. Encrypted messages look like random text.
Here are some examples and instructions. But GnuPG has plenty of manuals, on the same Web site where you download it.
I’ll look into that. Thank you. Hope it’s not incompatible with firewalls and anti-virus programs.