should have 3 hoses on your RO unit. A Yellow, Orange and Blue, right? If so, Yellow in supply, or incoming. from the cold water line under the sink. The Orange is the waste water. It goes into the drain and the blue goes to the tanks
Now, depending on what kind of plumbing is in your home, depends on what kind of fittings you need to adapt the RO lines to the house lines. And you need a shutoff on the Yellow line. The cold water is presurized, and without this shutoff, the RO will constantly run.