I was watching these posts by e-mail with mild interest until I noticed the phrase “I am trying to use this for secure journalistic purposes…”, when alarm bells began to ring. I can appreciate that it is essential that you figure this out, and are able to help your correspondents do so as well, and that you are sure you’ve got it right.
So first, as “Nippon Bill” points out, the security of your e-mail depends absolutely on keeping your secret,or private, key exactly that - secret and private. Only your public key is to be sent out across the Web, uploaded to a keyserver, or otherwise distributed to your correspondents. When you eventually establish the key-pair that you will actually be using seriously, as opposed to the one you are experimenting with now, you need to back it up securely somewhere, i.e. on a disk/flash drive in a safe. Otherwise if your PC expires or crashes, you may finish up with an archive of e-mails that you can’t read any more. And if your computer is compromised, your keypair may be stolen from it, so the backup file should be securely erased from your computer once you have it safely stored elsewhere. (Ideally you should have two backups in separate places. Yes, OK, so I’m paranoid. If you’re a journalist, so should you be.)
To learn how to communicate securely, using secure e-mail, I used the combination of the Mozilla Thunderbird e-mail client and its add-on, Enigmail (with GPG4win installed beforehand, which I guess you’ve already done). I thoroughly recommend that you do the same. There is an excellent manual on Enigmail, written by one Daniele Raffo of the Enigmail team, which takes you through the whole process, including a short section on Adele the robot. It’s so good that I actually sent Daniele an (encrypted) e-mail congratulating him on it, and received a very modest (encrypted) reply. You can find it here: https://www.enigmail.net/documentation/handbook.php. I downloaded the PDF and put it on my tablet, and continually refer to it, as well as the GPG4win compendium PDF. If I were you I would read the two in conjunction.
For Gmail webmail, you can use Mailvelope, which also uses OpenPGP encryption, so your keys also work with it, although you may have to import them separately into Mailvelope’s keyring - not sure, I’ve only just started using it, but overall it is simple enough. See website here: http://www.mailvelope.com/. For the Chrome browser you can install the Mailvelope extension from the Chrome Webstore, but for Firefox you need to download the latest extension beta from the Github project website - don’t worry, it works fine.
After you have gone through Raffo’s manual and tried Enigmail, come back and ask if you have any further problems. There are one or two fine tweaks that you might want to know about, but they only become relevant later.
If you decide that you just want to send encrypted text via Gmail without using the more secure methods of fully-encrypted e-mail, there is a way of doing that, via Chrome, here:
I made a comment on the site about the security of the encryption (which looks good - the encryption, not the comment).
For general encryption of sensitive documents on your computer, I recommend Truecrypt, here:
And recommended reading on computer security is anything by Bruce (Trust the Math) Schneier. (https://www.schneier.com/)