When you send your Dwellers out into the Wasteland Fallout Shelter, they'll gather resources for you without you even actively having to do anything. This means you'll want to do so whenever you can. To help you out, here's how to send Dwellers to the Wasteland in Fallout Shelter.
How To Send Dwellers To The Wasteland
To send Dwellers to the Wasteland in Fallout Shelter, all you'll need to do is drag them outside the Vault. From here, you'll click Explore. However, you're not done quite yet, as you'll want to keep up with your Vault Dwellers while they're in the Wasteland. Otherwise, you can risk them dying.
To keep an eye on any Dwellers who are in the Wasteland, you can click on the Wasteland up in the top left of your screen. Checking on your Dwellers is important, so you can know when their health is low or when you're ready to bring them back, which you can do just by clicking the button that says Recall. It's a good idea to bring your Vault Dwellers back when they've retrieved a few items.
Sending Dwellers to the Wasteland is a good idea when you're going to be playing for a while and can check on your Dwellers regularly.