Problems Installing Cryptlocker

[Moltke]

INDEED and those instructions were simply to do sudo apt-get install cryptkeeper encfs and it would install but as you can see from my screen shot above the system said nah!

The system "said nah!" because there's no cryptkeeper package in Ubuntu 20.04, it was available up to 16.04, Xenial but it isn't anymore. 

I want to password protect a folder

There are alternatives available and you probably don't need to install anything:
1. You can just zip that folder and add a password:
Select the folder and rigth-click on it, from the context menu select create a new archive or some similar wording. In the archive wizard choose zip as the output format, click on other options and add a password, finally click ok.
2. Make the folder hidden:
Rename it so it starts with a "."

Code:

mv folder .folder

now it's not visible unless you make it so.
3. Change its properties so only you can access its contents:
Select the folder and hit left Alt+Enter to open the properties dialog, go to permissions tab and where it reads others change to none, so nobody else can access it. Although, if this is a single user system, people may still get access to it, in which case your best bet is option 1.

Hope this helps!