How they add gases to high pressure tanks. Will the supply trucks bring it? And how will it be connected?
The original ISS design called for High Pressure Gas Tanks (HPGTs) to be delivered by the shuttle. With the cessation of shuttle flights, a system called Nitrogen Oxygen Resupply System (NORS) was installed.
High pressure resupply tanks called Recharge Tank Assemblies (RTAs) are now available to launch on visiting vehicles. These tanks are provided by the Nitrogen Oxygen Resupply System (NORS). The NORS consists of the RTAs, along with the Airlock Installation Kit (AIK) and Internal Fill Kit (IFK) support hardware to integrate the tanks into the existing nitrogen and oxygen plumbing in the Airlock. NORS can either support the oxygen and nitrogen systems directly or provide an equalization transfer to the external O2 HPGTs. The NORS RTAs are 48,263 kPa (7000 psia) oxygen and nitrogen tanks with a volume of 0.076 m3 (2.68 ft3). The oxygen RTAs are filled with 38.1 kg (84 lbm) O2 and the nitrogen RTAs are filled with 28.6 kg (63 lbm) N2.
The linked paper is very informative about the logistics of gas supply to the ISS. Also of possible interest:
Also, info about actual NORS ops since the first paper was written in 2015: https://www.nasa.gov/content/air-supply-high-pressure-tanks-ready-for-space-station