Well, there shouldn't be any problem to add all licenses to the existing license server service. To complete the activation process please paste the license key for each license - received by e-mail with the purchase (not the serial number). Please note, any time needed you can use Resend keys button under User Panel - My Licenses.
Let me mention, that there is a possible workaround by modifying system registry key to override the port and then manually configure all the clients and this way you can run multiple licensing services on the same network. That can be done by editing the LicservPort value in system registry. This value need to be changed on "both sides" correspondingly.
HKEY_LOCAL_MACHINE\SOFTWARE\Itoo Software\Forest Pack Pro
On the licensing server:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Itoo Software\License Server
If you decide to modify it, please remember you have to configure all clients by setting the network license to the IP of the server instead of finding it automatically. This can be done using the Change License Mode wizard after setting Network license mode in Configure the Network License window.
Anyway, we strongly recommend you to use just one License Server service per network. As mentioned above, you can add your licenses to existing license server service or separate your networks.