How to add jar into eclipse project

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Hello everybody!
Once I read an article where was wrote how to add jar's file into eclipse project.
When I followed this instruction it didn't work!
Instruction's snippet:
Open project's properties -> Java build path -> Add external JARs
and then you can use this byte code like this:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    
<!-- Path to our library -->
    xmlns:lib03="http://schemas.android.com/apk/res/com.template.library03" 

    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >    
    <com.template.library03.Component03
        android:id="@+id/component03"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="#FF0000FF"
    />
</LinearLayout>

My package name is com.template.library03 and component name is component03
But eclipse doesn't see the path to my library!
What am I doing wrong?
Please help me and sorry for my English!