• Click on the Settings -> Portal settings tab.
  
• Scroll down, and you would find an option "Allow screen sharing". 
  
• You can enable or disable it by clicking on the slide bar which you can find right beside this option.
  

• Navigate through, Settings -> Websites -> Live chat widget -> Chat window -> Configurations tab.
  
• Scroll through down, You would find an option "Display Screen sharing option".
  
• Enable or disable it by clicking on the slide bar right beside this option. 
  

After configuring,

• A visitor can stop sharing his/her screen whenever he/she wants. Same applies to the users.
  
• User as well as the visitor can swap their screens at any point of time during an assist session, but the latter would require permission from the former to do so, while former doesn't really require the permission of the latter.
  
• And if either of the end users (Here, end users refers to support members and visitors of your website) doesn't accept the request to share screen and if the other user just clicks on join, it would just be like waiting for the earth to shift its axis.
  
• And it's substantial that you understand the fact that this feature will not be available in the SalesIQ's free version. It would initially be available for the 15 day trial account and for the paid accounts. So do buy our product to avail this feature.
  
• But if you own a paid SalesIQ account but you do not own a paid Assist account, You might be allowed to handle one screen sharing sessions per day.