It means instead of buying their own computer parts, they helped themselves to the supplies at HP and Atari, where Woz and Jobs worked during the day. HP and A

It means instead of buying their own computer parts, they helped themselves to the supplies at HP and Atari, where Woz and Jobs worked during the day. HP and Atari probably didn't notice or didn't care. He's referring to when Apple was just starting out and they didn't have much capital.