There's another great utility available from the French company, IDRIX, called VeraCrypt. See: https://www.idrix.fr/Root/content/category/7/32/60/ . This is based on TrueCrypt, and can open TrueCrypt volumes. IDRIX claims that its utility has enhanced security features, which they concede come with the trade-off of encrypted files taking longer to open.
A helpful tutorial on how to use the utility is available here. VeraCrypt comes with a cool James Bond style feature allowing you to create a hidden volume inside the encrypted data. So even if someone forces you to reveal the password for the encrypted drive, partition, or file, your truly sensitive data can remain out of the hands of your foes. The 'free' space on any volume encrypted with VeraCrypt is always actually filled with random data, so there's no way to tell that there's extra space taken up with useful data. The hidden data is simply accessed with a password that is different from your decoy data.
VeraCrypt has you select both an encryption algorithm and a hash algorithm. The encryption algorithm encoded the data so it can only be accessed with a password. The hash algorithm allows the recipient to confirm that they have received the same exact data you intended to send.
An odd feature of VeraCrypt is that the wizard makes you generate the encryption keys by randomly moving your mouse cursor around on the screen . . .
A VeraCrypt file will appear as an extensionless file with the file size of the data you specified that it could be capable of holding - not just what you added.
The recipient clicks 'Select File' to browse to the encrypted file, and then clicks MOUNT to enter the password.