Well, you can't start on Line 14; that is, no matter where you start (unless
you press Enter multiple times to insert empty paragraphs, which you've been
told not to do), the first line of the document is going to be Line 1 and
will display as such on the status bar. The concept of starting at "Line 14"
is a pretty strange one, actually, and reflects the influence of a typing
background. It would make a lot more sense to say that you should start at,
say, 3.4" (which is Line 14 of a document with a 1" top margin and the
default formatting of Normal style), or that you should allow a certain top
margin.
I would first, if possible, clarify whether the teacher means Line 14 from
the top of the page (probably) or Line 14 from some specified top margin.
This will at least allow you to determine where Line 14 *is*. Without that
information, there's no way you can go forward.
Once you've established that, there are two ways to accomplish what you
want; both with require a little trial and error.
1. Add Space Before to the first paragraph. This is the easier approach. In
the Format | Paragraph, keep dialing up the amount of Spacing: Before until
the status bar shows the position that you determined is the correct one.
Remember to remove this Space Before from the following paragraph.
2. Add some Space After to the header paragraph on just the first page. To
do this, you'll have to check the box for "Different first page" on the
Layout tab of Page Setup, which will give you a separate First Page Header;
add space in this until the first line on the page is at the desired
position.
There's actually a third way that I sometimes use, though not just to create
white space. You can insert, before your first paragraph, an empty,
borderless single-cell table with row height set to Exactly the amount
required.