VPN configuration with drop in mode

Hi all,
I am implementing a pep link balance 510 with drop in mode and i need to set a site to site VPN.
there are 2 sites site A and Site B. site A is my main site and Site B is my remote site. And I am attaching the network diagram for your reference Kindly go through that help me to configure for this scenario
I need to configure the Site B users as to access internet through SITE A .

Thanks & regards
Sreedhar NC

There’s a send all traffic option on Speedfusion section which you can configure on your site B Peplink.

After that, with our more recent firmware version you can use a default route to point traffic to your core switch or firewall for routing.