I inherited this ferment tank in a load of home brewing equipment. I've never needed a lid with two inlets.. what's it for?
Without a picture, I'd guess you stopper one and use the other for the airlock during fermentation, and then when transferring, one is for the racking arm and the other to pump CO2 into.
OP, you need to use an image hosting site (like imgur) to post photos in the forum. Here is your image on imgur.
From the image above it appears there is a plastic valve which can be rotated to close off the two ports. As @MrOH discussed above, close off one of the ports and affix an airlock to the other (open) port). And I will be 'that guy', please thoroughly clean off that lid. Cheers!
