How to create own widget for adobe muse? So that I can add my own created widget in library to use it. What tools & ide required for it? If it can be done in adobe muse only then how?
You can't create complete new widgets for Muse. You can create embedded HTML/CSS/JS widgets with some UI for users to configure options by using the mucow widgets introduced with Muse 7.0.
The documentation for creating a mucow widget is here: http://adobe-muse.github.io/MuCowDocs/
If you have questions about building mucow widgets in Muse, the Muse forum is probably the best place to ask: https://forums.adobe.com/community/muse/adobe_muse_mucow_development