I have to find out site id in some other component like virtuemart and community builder.
Based on that site Id I need to do some actions(make change on that component) in that component.So what are the files need to include and how to get some where else.

You don't need to include any files to have the MULTISITES_ID defined present.
This defined is declared by JMS Multisites when this is a slave site.
As this is a "define", you don't need to declare anything to have the define present.
It is always present like a global parameter.

What are the features we have in using jms - virtuemart bridge.

As explained in the product detail
www.jms2win.com/en/joomla-multisite?page...33&category_id=1

This is a plugin that is a kind of bridge or gateway between Jms Multi Sites and VirtueMart when you want to propose a service to sale the website creation from the front-end.
In this case, in addition to create a website, you need to have a system where to place an order and proceed to its payment. In our case, we propose a bridge with VirtueMart to process the website creation ordering until its payment.
The bridge communicate with Jms Multi Sites to build the VM shopping cart and also process all the VM order status modification in aim to update the slave site status.

Hi,
In My case I have created the slave site from front end,It will automatically generate the database prefix as like u62slave11 but folder name as slave11.How to find the relation between this, is there any specific file have these details. I need this info for to make the url formation,I need to redirect the page based on site id.

It seems that you have defined a Site ID rule that use the {site_prefix} and the DB prefix that is u{user_id}{site_prefix}.

If your site ID correspond to the site prefix, you can rebuild the rule to get the DB prefix.

The relationship is the one that you have defined in your JMS Template rule and my analysis is correct correspond to the value that you have setup in your rule.

If you want to get more info concerning the site ID, see user manual chapter 4