I have existing vents for a hot air heating system in my house. How
are the connections made from a Central Air unit to the vent system ?

Thanks

Ed wrote:

I have existing vents for a hot air heating system in my house. How
are the connections made from a Central Air unit to the vent system ?

Assuming the vents and fan have been sized for AC, the condensor unit is usually
placed on top of / next to / below the furnace, before any supply duct splits.