The /tmp directory in FREESCO is in the ramdisk. So there is no permanent storage of files. As soon as you reboot the system the /tmp directory will be empty other than the current log that is created at boot time. Most if not all standard FREESCO packages are created to never use this directory other than to store pid files and other non essential files that are very small in size.
There is a manual way to force the /tmp directory to be a hard drive directory. Such as to create a /boot/tmp directory and then link it to the /tmp directory at boot time in the rc_user script. But you still need to add some other scripting to clean the directory as well at boot time so the directory does not have a bunch of unnecessary files in it.
The best solution is to figure out what program is using the space and re-configure it to use another location. Which we can do if we know what is using the directory.
If you are afraid that you might make a mistake. The chances are high that you will never learn anything.