mohdnasran
Let me explain a bit here about the integration of JA Builder and other template (here is JA Company). There are 2 ways for this combination:
1 - You have a menu item with type of JA Builder and assign that menu item to JA Company template style: this page will show header + footer from JA Company, the main part will be blocks you added via JA Builder
2 - That menu item has other types of content (for example, a single article or category blog, ...) and assign this menu item to JA Builder template style: with this case, the header + footer are blocks of JA Builder, but the main content will show the content of the menu item type and you can add blocks from JA Builder also.
So if you have a homepage already as our demo site, it's hard to put JA Builder block to it, you will need to build up a new menu item with one of above 2 ways and add modules / blocks as you wish.
Regards