Add-on in Softimage XSI (plugins in Softimage XSI)

[FreeFireBullet]

Hello everyone who work and start in XSI.
I am a newbie in Softimage and i am really confused how install and use add-on and plugins in Softimage.
I found many perfect plug-ins but i dont understand who it work,
Please anyone tell step by step process.

[sim3d]

use the addon in the File menufile:///C:/Users/Simon/Desktop/plugin_softimage.jpg

[sim3d]

use the addon in the File menu