Welcome to the forum crwright2020!
Can you give me what your Original Gravity was? I would think both kits would come in around 4 ABV.
There are a few things you could do to up the ABV.
1. You could add more Base Malt Extract (either Dry or liquid). This will not add any extra flavors, You can add 20% or more to up the abv
2. You could add a Specialty Malt Extract (usually only in liquid form). This will add extra flavors changing the beer. No more than 20% of total grain bill.
3. You could add Table Sugar or Honey (This can be turned into Belgian Candi Sugar to save money. Here is a good read about it.
http://www.homebrewtalk.com/showthread.php?t=42786) I have found that this usually mellows a beer. No more than 15% of total grain bill.
4. Lastly you could add Belgian Candi Sugar. (My favorite) Depending on the beer this can turn an OK beer into an exceptional beer. Adding hints of spices, accentuating hops, and changing the flavors in the beer. I make my own. No more than 15% of total grain bill.
Be warned that 2-4 have limitations and if you go overboard you run the risk of ruining your beer (Bitter Beer Face comes to mind). Since you are just starting out, the easiest thing to do would be increase your base malt extracts adding this at the beginning of the boil. Be warned, if you plan on adding any of the above Adjuncts, only choose one. Your total Adjuncts in a beer should not be more than 15-20% of the total grain bill.
If I were you, I would purchase two more of the same kits and modify them by adding one of the Adjunct's and then compare what the differences were and which one you like most.
Cheers
Preston