So as promised here is how to create an encrypted dmg. folder.
As you are running El Capitan I presume then the method has changed somewhat since Mavericks but I think it is actually easier. I made one just as a trial and here are the steps;
1. Open the Disk Utility app in the Utilities folder inside the Applications folder.
2. At the top of the desktop you will see the File menu in the Disk Utility menu bar.
3. Click File and scroll down to "New Image" and in the submenu select "Blank Image"
4. In the image below you will see "Save As" give this a name that is fairly innocent it will be the visible part of the folder. That is it will be seen if you put it in the Documents folder as a dmg. file with this name. eg. "My secret folder dmg." (a bit obvious huh?)
5. Let it save to the desktop for the minute you can move it later.
6. The next name is the name of the Disk. When you double click the dmg. it will mount what appears to be a Disk Drive. That is your folder.
7. The size is set at 100 Mb but you can type in what you like for example 1 GB. The size will depend on what you want to put in it. I like about 1 Gb myself.
8. Select the reccomended Encryption 128 bit from the encryption drop down menu.
9. You will now be asked for a password and to verify that password. YOU MUST REMEMBER THIS PASSWORD
9. Click "Create"
10. Now on your desktop you will see a dmg file with the name you gave it and a disk drive icon with the name you gave that. If you dont see it go to Finder menu > Preferences > General and make sure Hard Disks's and External disks are ticked.
11. Now double click the Disk icon and you will have a blank window. Go to the View Menu at the top of the desktop and select "Icon" "List" "Columns" what ever you like.
12. you can save to this folder like any other folder window eg. drag and drop.
13. Now close the window and right click on the Disk Icon and select eject. It will disappear leaving just the dmg. file. Double click the dmg. file and you will be asked for your password, enter it and the Disk Icon will reappear. Eject it again and drag the dmg. file to a safe place.
Now whenever you want to access your encrypted files click on the dmg. you will be asked for your password and the disk will mount and you can open just like any folder. DO NOT TICK THE "REMEMBER THIS PASSWORD IN KEYCHAIN" BOX or it will become like any other folder and will not require a password to open.
That's it!