While we can't just increase the power of natural light, there is something we can do. 

If you need more light, move your scene closer to the window. This will give you more light into your camera sensor, but at the same time, your shadows gets stronger. This is because of the fall-off of the light. 

On the other side, move your scene further from the window, your shadows gets softer and the lighting on the scene gets more balanced. 

Keep moving the scene while observing the shadows, and how the shadows changes while the intensity of the light changes too. 

Take any kind of white foam cards or white clothes and position them next to your scene. Observe how they bring the light back. You can use these if you want to increase the intensity of the light, or highlight some specific objects on the scene. 

The same with black cards - they behave as a negative fill. This means, they don't reflect any light back. This will make the shadows richer and your images gets more mood. 

You can download the guide below, to see how I use these tools in practice. 

Download this guide where I explain in real examples and Behind the scenes - how I create bright & moody, light & moody, dark images and images with hard light. 

Download this guide on this link.