Quick job Remote printing setup

We have our router setup TP-Link TL-WDR4300 v1.x with dd-wrt fireware. Got our printer connected with dlink 1020 print server as the printer is an USB printer. Couldn't get head around what ports needed to open so it'll available over internet. Plan is someone else can just add another printer and put our wan details to connect it as network printer. Do want to setup vpn or google cloud printer, just like to keep it real simple. I will give you access through team viewer so you can configure the router and dlink 1020 as needed.