I have instaled paltalk 9.1... questions are here:-
1.I want to video chat but I have no idea to use it.
2.is it free??

How can you have it installed it and not know if it is free? Check the documentation that came with it.
More here: Paltalk - Wikipedia, the free encyclopedia

I have downloaded from net then instal... yes I read that it is free... but when I start program uknown web page upload where they said me to upgrade by money.

That's probably the ad referred to in the link I posted. Best to go to their website for tech support.