Apache server question

Hi,

I have been offered free hosting on an Linux Apache server. Lucky me.
However, I have a public html directory created where i can put my site
on the server. I am to register the name against the primary and
secondary dns numbers of the server.

The owner will set the httpd so that my directory where the files are,
will be resolved as the home page of the site. Hopefully?

My question is do i set the sitemap.txt file in this directory? It is
the technically the root of my site.
The url in effect is e.g. http://joe.vapor.com/~gas/site/index.html.
This being the case I need to put a sitemap.txt file. Do I need to type
the urls in the sitemap.txt as it is or can I just have the urls as ?

I hope you understand my question. Basically i want the site to be seen
as http://mysite/index.html and not the apache server.

Thanks.