Hard to give advice without seeing the recipe. But most kits are much too lean on hops, especially IPAs, so adding some extra (within reason and with some diligence) will usually perk them up quite a bit.
Adding hops to the boil will increase IBUs. The longer they are boiled (or exposed to high temps) the more bitterness they add, but it's on a downward slope. Tinker with a recipe calculator (e.g., Brewer's Friend, it's free) to see how much your extra hops would add when "x" amount is added at "t" time.
The longer they are exposed to high temps the less flavor (and aroma) is left. Hence the importance of late boil additions, quick chilling after flameout, and doing 10-30 minute whirlpools/hopstands at reduced temps (150-180F) before chilling down to pitching temps.
Dry hops (in the fermenter after fermentation is done or about done) add mostly aroma but also flavor. Add them loose, they need to "swim" for best extraction.
No need for secondaries, just add to primary fermenter.
Avoid or at least limit introducing air (oxygen) to your beer after fermentation starts, wherever you can. Oxidation kills hop sensation.
