We have a R.O. cold water filtration system. We would like to install an Instant Hot (IH) water using the R.O. cold water as the input. How do we connect than and have enough water pressure to produce hot water?

You are likely going to need one of these RO Booster Pumps / Permeate Pumps - FreshWaterSystems.com

The outlet side of an under counter R.O. water treatment system is always piped in plastic, and, connected to a plastic tap / faucet. This is because RO water has such low ph, that it will corrode any metallic component that it comes in contact with, including - water heaters, bronze / brass / copper, and other metal alloys typically found in tanks, faucets, fittings, etc.. You should not directly connect RO treated water to any water heater, unless, you condition the water additionally via a neutralizer...