It's extrememly difficult to get someone somewhere they don't want to go - especially when they are paranoid.
I've only seen a few things work - and only sometimes. If the person has a spouse - the spouse enters therapy and in a few weeks, asks the disturbed individual to a session under the pretense that the therapist wants to talk to them about the spouse in therapy. While there, the therapist - who has to be "in on" this evaluates the spouse. Not all therapists will work under this sort of deceit, but sometimes, someone will see that some people really need a push for help.
The only other thing I've seen work is where the family gathers as many people as possible, and with the help of a trained intervention specialist, holds an intervention. An intervention is where all the family gathers after they have set up some sort of treatment - tells the patient how concerned they are about the patient and their illness. The point is to get the patient into treatment - and if they agree, they leave the intervention and go right into treatment - or for an outpatient appointment with a psychiatrist.
Other than that, I have not seen much else work - until the person's family all leaves them (like an alcoholic or drug addict) or they hit rock bottom themselves.