Cluster uses the Linux file permissions system that manages who can read and write what. A good explanation might be found here. If you are working with sensitive data, make sure you understand it and set the permissions accordingly.
How to set up a secure share between two (or more) users
Goal: I am USER1, and I want a directory (here named PROJECT_XYZ) that only me and USER2 can read and write to.
The easiest way to do it (without creating group, for which you would need the administrator) is using ACL (Access Control Lists), which is available only in /share/ directory.
Log in to the cluster.
Create the directory, readable only by me
cd /share/ mkdir PROJECT_XYZ --mode=700
Set it readable and writeable by the other user
setfacl -m "u:USER2:rwX" PROJECT_XYZ
Set the same permissions as default for all future files created in the directory