How do you scrap stuff outside of sanctuary?

[bad sniper]

I've seen guides for Fallout 4, and some of them tell you to scrap stuff in some place in Fallout 4 (Not in Sanctuary) But how do I do this? I'm only allowed to scrap within Sanctuary, and I need a workshop to scrap stuff. One example is, how do I scrap broken turrets in Diamond City?

[Joe Coffee]

There's probably a mod for it somewhere. Else, you'll have to mule everything that isn't tied down and haul it back to a settlement workstation.

[Aries the Grinning]

You can only scrap stuff at settlements/workbenches. For built materials only the build menu will let them scrap some stuff.
Outside of a settlement it's impossible to scrap, unless you're a bit savvy with the console and are willing to install mods that will mess up your game... So not for the novice or faint of heart.
I'm not sure what guides your are reading, TBH, the way described above is how vanilla works... anything else would need mods.

[Nite69]

You can only scrap within the settlement borders, however if you want to take the time you can pick up small items such as metal barrels outside the settlement border and drag them into the settlement zone to scrap them.

I also read someone using a rocket launcher to bounce nearby cars into the settlement zone so you can scrap them

[pathhiker]

use cheat codes....woops, did I just say that outloud...