How to Access Dreamweaver Website that was build in someone elses account?

Dreamweaver is NOT a hosting platform.  It's a code editor. 

You will need to contact your hosting provider and get the server log-in credentials to pull the site files off the server.   You can download the files with any free FTP client like FileZilla.

Once the site files are on your computer, you can edit them with Dreamweaver or any other code editor of choice.

Hope that helps.

to complete what @Liam Dilley said, I will add that 10 years ago, and depending on DW build, beside Template, there are others features that was somehow propriétary to DW and/or are plenty obsolete nowadays as... Library items, Jquery mobile, Widget, Spry library, Server Behaviors, ... well without seeing your website, and its volume, it is complex to say, what would be the better way to go... type in the clod and correct the code here and there with any code editor, or start again from scratch

Hi There,

It will not be anything to do with Dreamweaver. While the code may be generated using Dreamweaver template system you should not really need Dreamweaver at all unless you want too.

To access the site will be to do with where it is hosted.

Who is hosting the website, who has the domain and host login access information etc. Through that you can otbain or setup the FTP access details you need to FTP to that and pull down the files so you can then make changes and re-upload etc.