To unlock this achievement, like the description states you need to host and complete 10 games with custom presets, now it might not seem it but it's actually a little vague, first of all you can only create a game with custom presets in a player match, so you have to be hosting a player match in order to get this achievement.
So, from the Xbox LIVE menus select "Player Match" and then "Host", here you'll get to choose a game type and which map you want to play on, below that you'll see the preset option, select the preset option and you'll see you can edit them, go into that menu and edit/create your own preset, name it and then go back to that menu, cycle through the presets until you find your custom preset and then choose to use that one, simply host 10 games using this preset and the achievement will unlock.
Due to the online feature of this game being all but dead you may need to find a boosting partner, you can create a gaming session here;
http://bit.ly/gTa5Tf, you'll need a total of 2 players to boost this game.