Pay per view, via TiVo

[#1]

We have a TiVo box (and satellite box upstairs), with cable cards as tuners. No cable box.

I'm unaware of how to access pay per view. 

Anyone know how this is done, if at all? 

And if we have to have a cable box or boxes, how do they interface with TiVo?

[#2]

You need a Verizon set-top box to do On Demand with FiOS. You can use the providers app to access On Demand content  

[#3]

As stated above, FIOS does not support On Demand with cable cards.

You can get a FIOS STB, but it does not interface with any cable card device.