Redirecting OpenVPN Server routes towards other VPNs to clients

I have an openVPN Server that share a network in tun mode, the main network that it share is on the class : 192.40.190.0/24 .

The config file that I have on the Server is like the following :

local 192.40.190.8               ## ip/hostname of server
port 1194                        ## default openvpn port
proto udp
dev tun
server 10.8.0.0 255.255.255.0

#client configuration
client-to-client
client-config-dir /etc/openvpn/clients
persist-key
persist-tun
float

Now I have attached the server to another network card (eth1) where it is connected to another network 192.168.200.0/24 where there is a another gateway(192.168.200.15) to others remote networks 192.168.2.0/24, 192.168.3.0/24, ecc ...

The VPN server that have another IP address(192.168.200.99) on the second NIC, can reach all the others networks because it have a route table that allow it to connect all others networks through 192.168.200.15 gateway.

The question is : How can let the clients of the main VPN server (192.40.190.8, 192.168.200.99 ) connects to the 192.168.200.0/24 subnet and to the other networks behind the 192.168.200.15 gateway ?