I am a brand new Inkscape user. I have just installed 0.92.5 version. I have already downloaded Sizo software. I am not able to include Sizo as extension within Inskcape. I have read several instructions in Internet but they do not work. Can anyone please provide steps to follow so as to install Sizo extension in Inkscape? Thanks.

I do not use Sozi but for you I found two links that may help you if, you know about Sozi extension.

This link is to download Sozi also you can read the installation methods whichever is suitable for you. (if you already know then please ignore)

https://sozi.baierouge.fr/pages/20-install.html

This is the link which explain how to add Sozi extension in Inkscape.

http://haks-fedoraproject.blogspot.com/2011/09/sozi-extension-for-inkscape-to-make.html

It doesn't explains where to get .zip with extension.

In wiki i found that version 13.11 is the last version of sozi which is available as an Inkscape extension:
https://github.com/sozi-projects/Sozi/releases/tag/13.11