creating web space (internet file server) to store data over the internet or retrieve it from that PC to any other PC in the world follows the same lines as creating a self hosted website, although you arent creating a website, the principal is muc hthe same, i do it myself (but with a website as well) using a miple desktop computer at home..
first things you are going to need to do are:
1. contact your ISP and arrange for a static IP to assigned to your internet connection (if you dont have one already) anbd sometimes you have to pay for it, this gives your file server a SET WAN IP address and means you can access it via IP rather than using a domain.
2. obviously have the file server, and you will need to give it a static IP on the local network, as your ISP gave you one for the external WAN, and then you will also have to setup port forwarding so that any FTP ot specifit HTTP traffic points to the server and is forwarded and retrieved from there, but you will need software to do it, i use a neat little peice of software called WampServer (obtainable here: http://www.wampserver.com/en/download.php
this should enable you to configure as you please, download/upload/FTP setting to set up a web based storage option, and i must say it is very handy for a travelling tech like myself..
when it is eventually setup, you will use your static IP assigned to you by your ISP as a web address (eg. instead of www.mywebsite.com
you will use http:\\18.104.22.168 - this means you do not have to pay for a domain.. awesome!) this is a fairly involved process and if you dont know alot about it already.. i know you will by the time your done! once you have those 3 main things setup;
-static IP from ISP
-file server on network
i can help you out further with more specific instrctions and details if you like.. good luck!