Typically they are located in special folder. By default this is called "packages". This means when you get the sources from TFS on another folder and/or machine , you can not build the solution properly. You're missing dependencies.
So upload the package folder as well in TFS via the team Explorer you might say. That's is a valid solution indeed.
Another approach I found on a blog post (...) is to execute the nuget command-line executable to retrieve the dependencies.
- Navigate to folder <mySolutionFolder>
- ...nuget.exe install <myProjectFolder>\packages.config -o Packages
This will look for a file called packages.config, check the dependencies and download them if necessary into a folder called packages. This folder should be located on the same hierarchy when initiated. Usually beneath the <mySolutionFolder>
Maybe there are other (better) solutions when working with nuget? Let me know...