If you split the file in a text editor like ultraedit you'll see where each line adds a new entry into the database. Just be sure when you split the file to do so with getting the whole line in (don't break the entries on a line apart).
You might ask your host if you have ssh access. You can upload the file then use mysql commands in ssh to add the info into your database. I believe gizzy posted a nice topic at
www.ubbcentral.com on how to do this.