Resourcing is a different affair in Fallout 76 than in Fallout 4. Without settlers to work the fields, scavenge, or otherwise provide resources, players need to rely on automated extractors placed at resource sites located across Appalachia, in particular the claimable workshops at each of the settlements that players can claim. Extractors automatically generate resources and stockpile them as long as they're active - provided another player doesn't claim the workshop.
As usual, scavenging for resources is also a potent source of raw materials.