Ipsec and multiple subnets


I have Site1 with LAN network and a ipsectunnel to Site X, an external party with ipadress
And a Site2 with LAN network Here is a device Q that needs to be able to access Site X, via Site1.

I know how to setup a ipsec tunnel between Site1 and Site2, but how do I make Q be sending data to Site X ?

You set up the routes as described here: