Mikrotik Pc Router

[aamhm]

Hi ,
i have a problem on ,i'm newbie in Mikrotik Pc Routers ,i have 2 Pc Routers ,each one on a branch , i'd like to connect both branches .

so i can connect both Pc Router Over ISdn and they can ping each others ,but the two branches cann't c each others ,i need help

Each Branch Have it's server and it's own domain controller
server 1 : ip is 172.16.0.2 subnet mask : 255.255.0.0
router 1 : ip is 172.16.0.1 subnet mask : 255.255.0.0
Server 2 : ip is 172.16.90.2 subnet mask : 255.255.0.0
router 1 : ip is 172.16.90.1 subnet mask : 255.255.0.0

Router One can Dail Router 2 and connected
but both networks cann't c each other
so what can i do to make each branch can see each others ?
help?
i'll be really thanksful