I want to move from red rocket to the castle, but I don't know how, I already have settlers at the castle, but I want to move all my stuff like my 6 sets of power armor and other things. How do I move?
Fallout – How to move from settlement to settlement to another
fallout-4
Related Solutions
There are still a few options; Keep your best equipment and power armor in a depopulated settlement, such as Red Rocket truck stop. If you haven't sent settlers there, then settlers can't steal your equipment. Raiders may still be able to steal your things, but that's what all the turrets are for, right? ;)
Alternately, find a safe connected to a terminal, drop your stuff in it, and lock it. This has the downside that you'll have to travel back to wherever the terminal-safe was. And even if you can find or somehow create one in a settlement, settlers that have the hacking or lock-picking skill might still be able to get at your things.
Optionally, keep all your things in a region of the map inaccessible to settlers, such as a rooftop or closed-off upper floor with a welcome mat. This ensures that you can fast-travel to the area, while your settlers won't be able to reach it.
Redditor RandomVigilante made a nice (if possibly not 100% accurate) map of coverage.
You might want to check out the full Reddit Thread for more information on this map (including flaws, and possibly a Red/Green Colorblind friendly version).
Best Answer
There's no concept of a "home base" in the game, so there's no support for switching from one base to another.
You own both settlements, and have stuff at both settlements. In the eyes of the game, they're the same.
If you have some things you would like to move from one settlement to another, such as power armor suits or weapons, you'll have to manually move each piece.
Moving the Stuff
You could carry the items yourself, or you could get NPCs to carry it.
If you trade with a settler or companion in one settlement, you can fill them up with gear, then move them to the other settlement. Keep in mind that travel between settlements is not instant, so you might need to wait a bit for them to show up on the other end.
With rank 4 of the Strong Back perk, you can fast travel while overencumbered. If you have this, you can move everything but the power armor all at once.
Obviously, you can only wear one power armor suit at a time, and you can't carry them in your inventory. This means that someone will need to wear the suit to move it from location to location. Again, this doesn't have to be you. A companion following you can wear a suit, and won't drain its core.
I've had success putting a companion in power armor and sending them to another settlement, but some people have reported them showing up without the armor, so be cautious if you try this.
See this question for more information on moving power armor.
Supply Lines
You're probably aware, but just in case, note that supply lines can allow you to access crafting materials from connected settlements. Therefore, if you have supply lines, there's no need to move junk or other crafting materials like mods or crops.