Hi Shaik,
The following widget will help you to acheive Multiselect
https://marketplace.mendix.com/link/component/2295
Hi Shaik,
You should have in toolbox input reference set selector:
Or check this forum answers: https://forum.mendix.com/p/questions/11540474045298240
Plus for you documentation :https://docs.mendix.com/refguide/reference-selector
Regards, Serhiy