Get a battery box to hold them. The one I have is "Blue Sea" brand, but there are others available. Mine is specifically designed to hold two Trojan T-105 batteries. You will need a short piece of battery cable to join the two batteries in series. I bought a short one at an auto parts store, but I still had to shorten it and add a new connector fitting at one end, but it results in a tidy package without any excess cable. For mine, I bought a battery filler kit from Camping World when they had them on sale. That may be a bit of overkill, but it sure makes topping up the batteries a lot easier, and therefore more likely to get done. My 05 trailer did not come with a cut off switch, so I added one of those as well (Blue Sea brand again)
If you have the Iota Converter, you might want to consider buying the add-on "
smart charger" option, your batteries will appreciate it.