IPSec give clients a individual IP

Hi,

I want to give the clients that connects via VPN (IPSec) a IP over the Fortigate. The clients connect via Linux(strongswan) to the tunnel. How can I assign a IPv4 and IPv6 to the client simultaneously? I haven´t find a cookbook for this. If you cant assign it parallel to each other, that please explan how I can give the client a IP via Fortigate.

Greetings