Routing between 2 separate Fortinet routers

Hi,

I have a site with an existing Fortinet 100D router that needs to be linked to a Fortinet 60D router on the same site, but 2km away.

Configuration is as follows:

Building 1

Router 1: Fortinet 100D

IP: 192.168.1.1/24

Fiber connection out of Fortinet 100D (currently to managed switch port at Building 2 (pass all VLANs), then copper (pass all VLANs) to port in 60D. [Not sure this is correct way to connect?]

Internal network consists of

VLAN1 192.168.1.0/24

VLAN2 192.168.2.0/24

VLAN3 192.168.3.0/24

VLAN4 192.168.4.0/24

Building 2

Router 2: Fortinet 60D

IP: 192.168.20.1/24

VLAN1 192.168.20.0/24

VLAN12 192.168.21.0/24

VLAN13 192.168.22.0/24

VLAN14 192.168.23.0/24

I need to get traffic from Building 1 VLAN 3 & 4 to Building 2 VLAN 13 & 14.

What is the best/correct method to do this?

I don't want to just forward all traffic, ideally it would just be a few IPs.

Thanks,

Alex