I'm not able to add manually files to quarantine. Seems that there is no option to do that from GUI...
I want to add files that I belive is malicious but not detected by f-secure to quarantine.
It should be a option to send files to analysis directly from quarantine.
Why do you want to add malicious files? Even if you think your AV can detect and fix it, it will still have a risk of having your system penetrated.