Hi Tonybones,
You have come to the right place, best Cannabis forum on the web.
Your set up sounds good, do you have ventilation ? They do enjoy the fresh air and air movement in the room from an oscilating fan will strengthen their stems and keeps mould at bay.
One of the easiest ways to water is to pick up your pot when its dry and feel the weight, its not an exact science, just gauge how it feels then water until you get water running out of the bottom then leave it, usually a few days at least, pick the pot up again and gauge the weight, when its feeling close to that original dry weight, water again, you don't want the pot to totally dry especially with young tender plants, it will kill them. They want to be mostly dry but definitely never bone dry.
Another easy trick is to put a finger in the soil up to the first knuckle, if the soil still has sufficient moisture to sustain the plant the soil will stick to your finger, if it is dry and falls off it needs water.
Only give it plain PH adjusted tap water, Im not totally sure but I think its 6.5 for soil, it seems for the most part they do not require feeding untill the cotyledons (1st little round leaves) have shrivelled, they are kind of the yolk in an egg sustained the chick until birth.
Once they have shrivelled start feeding at about a quarter the maximum recommended dose, autos are very sensitive to chemical fertilisers, I have discovered this the hard way.
All these sections on the forum have 'stickies' threads that cover all the basics that are required reading for a successful grow.
Happy growing buddy, I hope it goes well, ask all the questions you want, very helpful, very knowledgeable folks on here and read as much as you can.
All very informative and many will answer your questions before you need ask them.
Also, try to leave your tap water to sit for at least 48 hours before use, it allows the chlorine and other nasties time to evaporate before use, its not essential but better if you can.
I have a couple of 25 litre beer fermenters for my water to sit in and it allows it to be at the same temperature as your plants.