There are several ways of accessing Raspberry Pi files through the network. One of the preferred methods is to use the Secure Copy (SCP). It is a file sending command allowing transferring data over SSH. This is a secure way of sending files between Raspberry Pi boards or other Linux machines. To use with Windows, you need special software like WinSCP.
As you can see, it requires additional software to access files from windows. But if you are used to transferring data via FTP, you have another option – SFTP, an FTP with encryption. SFTP is already enabled in Raspbian and can be used right away. Be sure that your FPT client supports sftp protocol. For instance, FileZilla, Bitvise, and the same WinSCP clients work without a problem. To connect to Raspberry Pi via sftp, you need to enter an IP address and port 22. Log in by using your connection credentials that are pi/raspberry by default. Once connected, you can drag and drop your files in and out.
If you want to move a bit forward and connect to sftp server from outside of your local network, you may need to use port forwarding on port 22 — more on port forwarding here.