How to use multi select field?

Please share some source from where we can get help to integrate multi select field in form.

I would like to share with you guys that using a multi select field is very simple easy to integrate within forms or nay where in web page. You can refer to the below shared URL from where you can see multiple types of multi select fields which you can use as per your need:

https://harvesthq.github.io/chosen/#selected-and-disabled-support

You can click on downloads button and you will see three zip sources but you need to click on "chosen_v1.8.7.zip" it contains advanced multi select fields which you can use following the guidance in the source code.

You can refer to below screenshot for your reference: