This is either 1 of 2 things.
1. You purchased a 35w kit and expected more (even though the 35w are usually bright enough for most people) - If this is the case, we would recommend upgrading to a 55w system if possible.
Keep in mind your headlights will also play a major factor in this. Are they old, foggy/hazy? If so you will want to get new ones or get them restored. If you have blacked out headlights that will definitely affect light output as well. Another thing to consider if you have a tinted front windshield, the light will seem dimmer by default even though it isn't. These are all things to keep in mind.
2. Number 2 and usually the most likely; is that your headlights aren't angled correctly. For trucks this doesn't seem to be an issue but for cars especially "low" cars it will. Chances are your headlights are angled downward, park in front of a wall and turn your lights on, if they seem low then they likely are. Pop the hood, grab a screw driver, and there's usually a screw above the headlight somewhere and when you turn it you should see the lights go up/down. Use a tape measure to get both sides even or how you want them and you should be good to go after that. If you're worried about blinding oncoming traffic then keep the driver side slightly lower - as this the light oncoming traffic will be hit by the most. (See the phenomenal difference below)?
Top = angled downwards (factory)
bottom = angled upwards a tiny bit (2 minutes of total work time)