From the previous article you learned how to build an SWC file.
Next Step is to build the MXP for the Adobe Extension Manager to install the component which you have made(SWC). Abobe Extension Manager allows you to create MXP file with the help of MXI file, MXI is nothing but, it is a simple XML file which contains some informations about the compoent. Like, Author Name, Component Name, Version, Description, Files etc.
Ok, lets start with the help of some screens. 
Create the MXI as shown below and save it as you componentName.mxi. (Note: Please make sure that your swc file is in path that mentioned in MXI file)
MXI XML file:
<?xml version="1.0" encoding="UTF-8"?> <macromedia-extension name="Square Box" version="0.1" type="component" requires-restart="true"> <author name="Midhun Devasia" /> <products> <product name="Flash" version="9" primary="true" /> </products> <description> <![CDATA[This is a sample component. TutorBoy.com]]> </description> <!-- Describe where the extension shows in the UI of the product --> <ui-access> <![CDATA[Acces the component via Components > YourComponents Etc. ]]> </ui-access> <!-- Describe the files that comprise the extension --> <files> <file name="SquareBox.swc" destination="$flash/Components" /> </files> </macromedia-extension>
Open the Abobe Extension Manager and goto File->Package Extension
Open the MXI file
The the Extension Manager Automatically convert the MXI file as MXP and it will ask where you want to save it.
OK, Now you created the MXP pack, and it is ready to install .
How to install with Abobe Extension Manager.
Open the Abobe Extension Manager or Double click the MXP file and it will open-up in the Extension Manager. 
Accept or Decline option
You will get a Success Message from Extension Manager once the installation is success.
Ok Perfect, now check the Extension Manager, you can see the extension over there with you name as author, and so on…
Excellent work!! the post was very useful.. i was actually searching for a easy to understand tutorial cos i am new to this!!.. kudos mate
god bless you.. n keep posting
I’ve copied the MXI code and can package it into an MXP, but after installing it the SWC is not in my Flash IDE installation directory nor the components library. Extension manager says Square Box is installed but no SWF exists. Anyone else experience this problem?
Correction — no SWC exists after the package is installed.
Talk about reviving something old, but since I based my package on this tut, I figured I could try and get some help here =).
I have about five custom components that I have been able to compile into an MXP file, and install to the Components directory. However, when I try to test one, I seem to get some errors, because the components start doing that “error flashy/flicker thing”.
I have tried packaging the sources, and installing them into the $flash/Classes folder, tried $flash/Components (along with the FLA), and numerous other folders while scouring the net on this issue.
Here is how I *THOUGHT* it should be set up in the MXP, but this is not working. However, If I run a test movie, and put the sources directly in the folder with my test FLA, everything is fine, so for some reason, no matter where I put the classes during installation, it just can’t find them.
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For the record, though, all of the installation works just fine; I can find the sources and FLA in the requested installation paths, but it seems that the components cannot find them at runtime.
Thanks in advance for any advice you may have.
Awww, you’re kidding, it won’t let me post the code. Hmm, well I hope at least that my problem is clear.