So this watch does not need a battery?

hello nikki. thanks for interesting. yes this is automatic mechanical wristwatch. no need any battery at all. please watch out the other merchants who are following my listing. they're setup a cheaper price lower than $16.50. but they were just send the different version to you. like as hand-wind mechanical only. not "automatic". you can check out the back case you will know about that.

How often do I have to wind the watch after I do it the first time?

You don't have to wind it, you just put it on and it winds itself with your activity. If you don't wear it all the time you will have to put it on and it will wind itself with your actions. Depending on how long you leave it off (over 24 hours) you will have to re set the time.

Is this watch water resistant and does it have a mark to indicate it is water resistant

It has no markings indicating it is water resistant. I would guess that it would not survive being submerged but I have gotten it damp from washing my hands and it still works great.

how do you set the time? The knob does not pull out

Dear customer. if you received a defective watch. please go to your order page, and click the contact seller to send message for help. if you place an order with us(GuTe trade). I will offer you free replacement. because my listing got many others following but some other seller IDs may selling the low quality watch. or send the hand-wind version(cheaper) to you.please note!!