@Mustang_Bobby weren't you also the one posting a few days ago about the cheapest, most basic alcoholic beverage possible? I see a trend forming...
But, your options are basically:
1) Add sugar. Just corn sugar or plain ol' table sugar will do. ABV goes up, body gets thin. Might taste hot (alcohol burn) or cidery if you overdo it.
2) Add DME. Lighter is better to avoid really messing with the flavor profile, but things will still be "different".
3) Scale up the recipe. Add DME, but also proportionally increase steeping grains and other ingredients. You might preserve the intended flavor profile, but this is going to be more expensive, and difficult if you only have access to kit beers.
4) Skip the kit and move on to recipes that match the character you want. See the last part of #3.