I\'m looking into a system where users can upload xml files to a website for others to download later on. I have very little experience in this department and don\'t really
Yes, you will need some form of hosting for a web site/service. The site/service must accept the submission of the XML files. There are lots of ways of doing this depending on quite what you want and the security you wish to implement. Your web site/service must also provide a way for the user/application to browse and download the said XML files. Again there are lots of ways to do this and again security may be a consideration here.
I'd suggest investigating the options available/desirable to you and then asking more specific questions here.
Update
With regards to what you'll be doing on the phone. You'll probably want to POST the data from the APP using HttpWebRequest.
The easiest way to get data from a server is using WebClient but depending on security you may need to use HWR.
If you don't have any hosting then what you get will likely impact what you can do. The security of the data transmitted and how it is stored will impact what you need to do.
I'd start by investigating/researching the basics of HTTP.