The bell will need to be powered, so construct a power source too if you don't have one nearby. Build a red and blue arena pad relatively close to each other, and then place a quitting bell nearby.
Find some empty space in a settlement that has several settlers or companions, and enter the workshop menu. This is by far the easiest achievement of the 3, and simply requires you to pit two settlers against each other in a hastily built arena. Requires: Steel, Wood, Copper, Circuitry, Glass So continue to do this, just don't cook the food when preparing to go for these achievements. I mentioned in the general hints and tips to grab food when possible, and cook it for XP and health. This will save time when it comes to working on this DLC. I've listed the food required below, but as recommended above, it might be worth playing the regular game for a while and just hoarding these when you come across them. If you haven't already grabbed the copy of Wasteland Survival Guide from Sunshine Tidings Co-op (directly west of Lexington, by the map edge), now's the time to do it, as it will allow you to collect more meat from killed animals.