Could someone post an example of how to use a starpoint in CADSTAR?

Could someone post an example of how to use a starpoint in CADSTAR?

And how big must the pads be on the component/footprint for the starpoint?

It is a two (or more) pad component with both pads the same and in the same position, they can be surface mount or PTH pads. They can also be any size you want.
They are used to connect two different signals together at one point (the starpoint), so you create a two (or more) PINS, connect your nets to these pins and then you can join the nets together on the PCB without any design errors.
Quite often used to join two grounds together (!) or for a thevorin connection to a point on a voltage plane or resistor pin, etc.

Star points are not connecting with two various signals by copper pouring in same electric layer.
(i am having two different ground signals say agnd and cgnd and used two templets for each ground signal,
but when i copper pour only one signal is getting shorted to starpoint, but is i copperpour in different layer there is no issue).

Please suggest.

You can only pour copper from one signal over a starpoint, because starpoints do not work like you think for pouring copper.

They work by the first segment of a track exiting them not being in error when it breaks design rules or touches another signal that also connects to the starpoint.

This is for the first segment.

A copper pour has lots more segments so it does not work the same way.

N.B. If you track into the starpoint it will not pour over it.

Make yourself a big starpoint, you can make 1" pads so can make the starpoint a big rectangular pad that can join 2 copper pours together.
It would be better to manually add copper either side of a big rectangular starpoint than try and pour copper onto it, the manualy added copper can then have poured copper overlapping it.

They can work very well when you understand how to use them best.