What is a good way to transfer files from a windows 7 computer to a new windows 8.1 computer? I can't find the "file transfer' function.

Use Windows Easy Transfer. This is under All Programs, Accessories, System Tools.  This will backup all your files saved in common spaces on the Windows 7 computer, and any themes you have applied and changes you have made to your personal profile.  Once those are saved, you can apply them with the same tool on Windows 8.1.  You can do this through a network transfer as well, if both computers are on the network.  This is a quick and easy way to transfer the files and settings over.