Here’s how to encrypt a single file using a password and a salt:
openssl aes-256-cbc -salt -in filename -out filename.enc -base64
Type a strong password when prompted.
Here’s how to decrypt the same file:
openssl enc -d -aes-256-cbc -a -in filename.enc -out filename
You’ll need to re-enter the passwod that you used to encrypt it.
If you want to encrypt multiple files, combine them into a tar or zip archive before encrypting them.