Creating massive, custom settlements is an awesome addition to the "Fallout" franchise.
But while settlements are useful for gathering all your resources in one place, it's generally more helpful to access your stockpiles of goods from any settlement: That way you won't lose time constantly traveling back to the same town just to drop off some junk or pick up a weapon.
To connect your settlements in "Fallout 4," you'll have to create what are called "supply lines."
Supply lines can only be established once you've reached the sixth tier in the "Charisma" upgrade tree, which showcases the Local Leader perk. You'll need the first rank in that Local Leader perk to get started.
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Once you've met those requisites, go find a settler at any one of your settlements. Then, activate your workshop menu - the button you hold to start building resources for your settlement. If you highlight over one of your settlers, you should see a "Supply Line" button option. Once you click that button, you'll get to choose which settlement to send that settler to.
And that's basically all you have to do!
YouTube/Dat Saintsfan
YouTube/Dat Saintsfan
To view your supply lines, check out the map on your Pip-Boy and you'll see an option (highlighted at the bottom of the screen) to "show supply lines." Click that and you'll see all your supply lines light up, which will let you figure out which settlements still need to be connected:
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You can create supply lines between any settlement, but you'll need different settlers to connect all your settlements. If a settler is already en route to a settlement, don't send them to a different settlement or you'll break the supply line you already have.
If you've established a supply line but your settler hasn't arrived in town yet, just sleep for a few hours (find a bed and choose the number of hours you want to stay) and then fast travel to the settlement you want to upgrade. Your settler should have arrived by then, which will allow you to start building up that remote settlement with all the resources you've collected in the original settlement.