Well... that all depends on how much information you provide, so far it isn't enough. Ebb and flow works off float systems if you are talking about a system with individual buckets, 5 of them actually and 2 pumps, one in the reservoir and one in the controller. If you are talking about flood and drain, which is much easier, then you can view an explanation of how to determine that, its post number 48 in my blues thread. The number of times you would water will be dependant on the medium you use, I think most use hydroton with the ebb and flow, I use coco, Al B uses foto cell and a little flock rockwool. etc.
If you give us more information we might be able too help. VV