It depends on whether your site is hosted on a UNIX system or Windows system.
Your webmaster should know how to do this without your needing to tell them--otherwise they are not a webmaster.
In any case:
On a UNIX system you need to tell your webmaster to set up an .htaccess file. The .htaccess file is a plain text file that goes in the root.
If the entire web site has moved, you can do a single redirect that sends all visitors who try to go to the old location, to your home page at the new location:
Or you can do individual redirects to send visitors to specific pages to the new location of that page:
If the original file was in a folder, the redirect includes the path:
I have information about 301 redirects on my blog at:
http://internetresults.blogspot.com/...-redirect.html
If your web site is hosted on a Windows system it is a little more complicated. The changes need to be made in IIS, and that is usually done by the system administrator. If you need to know about IIS, I can tell you more.