Follow these steps:

1. Open your document  library.
2. In the left menu, select Modify Settings and Columns.
3. Under the Columns sections, you will see a list of existing metadata fields
or properties. By default, only the title field exists.
4. Click the Add a new column link.
5. Enter the appropriate information for this metadata field.
6. Click the OK button.
7. The new metadata field is now added under the Columns section.

I have a doughty in sharepoint, how to open a link in
new window. Already I have a web part in that I have
given a link e.g. http://www.hotmail.com now the
problem is that it’s opening in the same window. But I
want it to be opened in a new window.

I suppose you are referring to the sharepoint document  library, and not the
backward compatible doc library. You can go to the document library setting to
add/remove the properties. Bear in mind that the concept of "document profile"
does not exist in the new version. You can add extra properties to doc
libraries, and you will be able to search with the new properties. The downside
is that you have to do it to every one of libraries, instead of defining the doc
profile once.

I am new to Sharepoint and we are using SPS 2003¡ I may be
misunderstanding you. I think you could just define the properties by adding a
column in the DataSheet view and then Save that library as a template (Under
General Settings). This would add this template as an option when you create
Document Libraries. You could also edit the Submit/Edit Forms before saving as a
template if you wanted to. Of course this will not change existing Document
libraries. You would have to edit them in the Data Sheet view.