From the error message, you have also filled in the "Stimulus File" field in the Setup->Simulation Files form (as well as on the model libraries). The error message you show happens if you have got the path incorrect or the permissions are such that the file cannot be read.
You don't need to specify it on the Stimulus File field and the Model Libraries - one is enough (otherwise it will get included twice), but in either case you need to ensure that the pathname is correct. In a UNIX window, check:
ls -l /home/HuanNV/Desktop/oppoint.scs
Does it exist? Is it readable by the user in question? Try doing "cat" on the same file to see if you can read the contents. If you only specified it on the Model Libraries form and the file didn't exist or wasn't readable, you'd get a message in the simulation log file:
Error found by spectre during circuit read-in.
ERROR (SFE-868): "input.scs" 10: Unable to open input file `/home/HuanNV/Desktop/oppoint.scs'.
No such file or directory.