The company has 'plugged into' the international market. [=the company has become connected to the international market; the company has begun to do business in the international market]
His friends are 'plugged into' the city's music scene. [=his friends are actively involved in the city's music scene]
The computer program will take data from these sources and automatically 'plug' it 'into' the equation.
(..) All I can think of is they must've wanted the alien for their weapons division. He's been protecting it right along. Parker, will you plug it in? - I don't know why... - Because he may know how to kill it. Ash, can you hear me? Ash? Yes, I can hear you. (..)1979 Alien
(..) Good morning, Mother. [Voice Over Radio, Indistinct] - Right. - Okay. Plug us in. Thank you. - Where's Earth? - You should know. It's not our system. Scan. (..)1979 Alien