Try to do the following.
Go to the properties tab of the folder or folders that you want to restrict the access to. Under the general tab, click on the advanced button. There should be an option to encrypt your files. Enable it, and now you are the only one that can open the files.
Or you can try the following.
Enable Simple File Sharing. This will allow a security tab to be dislplayed under the properties of folder. You can then add, users and set the restrictions that they have on those folders.