Just go with plain water for now. Until they get bigger they'll be okay with plain PH balanced water. Check your water for chlorine and contaminants if possible. I used to buy filtered water (not distilled) until I got my own R.O. Setup
When your plants start to get tall and healthy Follow the instructions on the bottle. but start small.
For example if it says "use a tablespoon of fertilizer to treat 1 gallon of water" start at a quarter tablespoon" try that for a few feeds.
Then bump it up very slowly. Half TBS-three quarters TBS...etc...
If the tips of the leaf start to turn yellow or "burn" it's too strong, feed with plain water until she greens up again. And then you know how strong she likes the nutes your using.
You water when she's thirsty, when the top soil starts to dry. If your soil is constantly soaked that's not good... she'll start to slump when she's thirsty, or over watered. Make a note of how much water you use and how long it takes her to slump and want more. Feed before she slumps. If you let it dry out a little before feeding the roots will expand in search of more water, and that's good!
Watch "ready set grow" on YouTube a few times to get the basics. That helped me when I was a newbie. I watched Jorge Cervantes ultimate grow DVD 1 & 2 which is available on YouTube but some of his methods and information is a little out of date. Nonetheless, it's where I started!