How do I..set this route/bridge up?

RouterOS Wireless Networking
1

DS3 Internet —>ciso router -->RB112 <–5g link → rb112
–ethernet –
rb112 <–5glink–> rb112.

From our office to the relay tower and then from that tower to another. I assume I will connect the two rb112’s with a cross-over cable on the ethernet ports.

2

Looks it is possible.
What is your problem?

Maybe you can try using 1 RB112 with 2 minipci, or if you need more bandwidth, using one RB532 with 2 minipci.