Hi. My name is XXXXX XXXXX I will help with this.
Do you have multiple user accounts and switch between them or do you both use one account?
If you use fast user switching, then you can both have an account (make a new user on the Mac) and Log out/in for each user or 'switch' between them. Difference between the 2, not much, fast user keeps all users logged in, but only one at a time can use it. Log ot and log in is the better way as it shuts down each user to load the next one. This restricts the user to their own space.
To do this go to System Preferences and create a new user. Make it a standard user. then go to Login Options and click on Fast User Switching. Close the pref pane.
When you are logged in,you can also make a screen saver that comes on fairly quickly and then set a password XXXXX it. Not the most secure, but it does stop the casual user from getting a peek.
Or, you can do a get info on the folder and then set permissions. Make it read/write for you (owner) and write only for the other two. Again, this stops the casual user from seeing in, but you need to have 2 users on the system.
Or, you can make the folder invisible. Here
is a very good article on this method.
If this helps, please click Accept.