I've been googling this but can't really find the answer. From what I can tell, you can load images to the server. But what I'm trying to do is make dreamweaver grab the images from the server instead (so not from my local folder). I already set the FTP up in dreamweaver and made sure it shows correctly.
I am not too familiar with Dreamweaver but I am pretty confident you're coming at this with a wrong set of expectations due to missing understanding of the fundamentals.
FTP stands for File Transfer Protocol and is used for exactly that: it transfers files. Therefore you can upload files to the server and download files from the server. You can not access the files directly from a website, that's what HTTP (Hypertext Transfer Protocol) is for.
So, what is absolutely possible is to hard-link the server files via their URL to your local development environment. This is entirely independent of the software used and amounts to the extent of what you can do.
You may be able to set up a little convoluted scheme via mounting the server folder via FTP to a local folder. This folder would then behave like a regular file system folder (albeit very much slower) and given the correct location, you could very well get the files directly from the server. But again, this is independent of Dreamweaver.
There is free software like curlftpfs when you're comfortable with the command line. Seeing that you use Dreamweaver, I venture a guess that you're not. There are commercial GUI alternatives like Mountain Duck (Win/macOS), ExpanDrive (Win/macOS) and Transmit (macOS) that can do what you need quite well.