In order to upload or download files you will need to utilize what are called file transfer protocols. File transfer protocols are used to handle the transfer. They make sure that an accurate copy of the file gets transferred. They all do the same job of transferring files between computers. In Windows 95 and newer the default transfer protocol is Zmodem.
Some computers can only do one or two file transfer protocols.
Check your communications software manual to determine which file transfer protocols it will execute and the commands needed to execute them. If possible use Zmodem. It will transfer files faster than any of the others. However, any will work. From the Main Menu select F File System.