I'm currently caring for a black caapi. I wanted to know exactly how much light and water to give it. I've found a lot of contradicting and vague information so far. I've been keeping the soil wet and giving it indirect sunlight. When I put it in direct light the centers of the leaves turned brown. They seem dehydrated so i concluded it was sunburn if I'm wrong please correct me. Due to the visible damage I wanted clarification on ideal environment so I can avoid any further stress.

Dehydration and sunburn are two completely different things. The former is a lack of water, the later is UV damage.
Caapi should be able to take any amount of UV it can get anywhere at sea level, although if it has been grown out of direct sunlight, it may need time to adjust and may drop most or all of its leaves before it grows new, UV-resistant ones.

It does like a fair amount of water and if you're growing it in a pot indoors, keeping it out of direct sunlight may be more practical as it reduces the frequency of watering needed.

How often should I fertilizE and with what's?

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I fertilize little caapi, I prefer to make a good mix of soil that contains all the nutrients for them at least to start fertilizing the first year.
  but if so I fertilize with cow manure tea, hummus tea, for nitrogen use coffee byproducts, or liquid hummus, only fertilize every 15 days as they are very prone to overfertilization.
On the other hand, I only fertilize when some lack is noticed,
they are usually very good nitrogen users
  so to have a leafy bush I recommend LABS

I have mine growing in the ground. Here the 'soil' is pretty much bare sand with some leaf litter on top of it.

I never fertilize them and they overgrow the space I have for them every year.

My caapi is thriving. Thank you for the advice. It seems to love the nitrogen only fertilizer I used.