How to enable XML editor option in AEM ?

Hi @mayursatav ,

Analyzed thing as below, as per my understanding 

That's XML Add-on available in Software Distribution, you have to install and setup.

• Prior & up to AEM 6.4.0 that was XML Editor and the Add-on is as below
• From AEM 6.5.0 onwards, Add-on is placed under Tools that is - XML Documentation      

Refer below guides for more details: 

1. https://helpx.adobe.com/content/dam/help/en/xml-documentation-solution/3-6/XML-Documentation-for-Adobe-Experience-Manager_Installation-Configuration-Guide_EN.pdf
2. https://help.adobe.com/en_US/xml-documentation-for-adobe-experience-manager/index.html#t=DXML-master-map%2Fintro.html
3. https://experienceleaguecommunities.adobe.com/t5/xml-documentation-discussions/4-0-release-for-xml-documentation-solution-is-now-available/td-p/432955

Hope that helps!

Regards,

Santosh

Refer 

https://experienceleague.adobe.com/docs/experience-manager-xml-documentation-learn/videos/getting-started/understanding-the-aem-user-interface.html?lang=en