I want to install an outside light with pir, the nearest power supply is from a lights switch,?

I would find worthwhile an idiots guide to help me run a cable from an existing light switch, to another switch (that will operate the outside light) then to the O/S light itself.
I have tried to connect the light exactly to the existing switch,

an idiots direct is get someone who knows what they are doing!

otherwise you know what you are doing and can forget the idiots guide.

Why does my PIR sensor-controlled light stay on constantly?

Yesterday, I was maddening to work out where the main switch was for my outdoor security light which works with a PIR sensor. This was already built into the house I bought so I had to experimentation. First I 'switched on' the light by putting my hand

Quite have a two way switch.

Pir Light Switch - News

ITB Students Unleash Creativity With Innovative Electronic Devices
His sketch uses a PIR sensor switch as a mode selector and interfaces with PIC PIC16F877A and can be implemented in a wide range of applications such as